Chitin and chitosan: Properties and applications
ARTICLE IN PRESS
Prog. Polym. Sci. 31 (2006) 603–632 www.elsevier.com/locate/ppolysci
Chitin and chitosan: Properties and applications
Marguerite Rinaudo
CERMAV-CNRS, affiliated with Joseph Fourier University, BP53, 38041 Grenoble Cedex 9, France
Received 26 January 2006; received in revised form 13 June 2006; accepted 20 June 2006
Abstract
Chitin is the second most important natural polymer in the world. The main sources exploited are two marine crustaceans, shrimp and crabs. Our objective is to appraise the state of the art concerning this polysaccharide: its morphology in the native solid state, methods of identification and characterization and chemical modifications, as well as the difficulties in utilizing and processing it for selected applications. We note the important work of P. Austin, S. Tokura and S. Hirano, who have contributed to the applications development of chitin, especially in fiber form. Then, we discuss chitosan, the most important derivative of chitin, outlining the best techniques to characterize it and the main problems encountered in its utilization. Chitosan, which is soluble in acidic aqueous media, is used in many applications (food, cosmetics, biomedical and pharmaceutical applications). We briefly describe the chemical modifications of chitosan—an area in which a variety of syntheses have been proposed tentatively, but are not yet developed on an industrial scale. This review emphasizes recent papers on the high value-added applications of these materials in medicine and cosmetics.
r 2006 Elsevier Ltd. All rights reserved.
Keywords: Chitin structure; Chitosan structure; Chitosan derivatives; Biomaterials; Chitosan-based materials; Cosmetics
Contents
1.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
2.
Chitin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
2.1.
Chitin structure in the solid state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 604
2.1.1.
Crystallography of chitin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 605
2.1.2.
Reversible and irreversible intra-crystalline swelling of chitin . . . . . . . . . . . . . . . . . . . . . . . . . 606
2.1.3.
Infrared spectroscopy of chitin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 607
2.1.4.
13 C CP-MAS solid state spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 608
2.2.
Solubility of chitin and chain characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
2.3.
Chitin derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 610
2.4.
Applications of chitin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
3.
Chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 611
3.1.
Chitosan structure and characterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612
3.1.1.
Solubility of chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 612
3.1.2.
Degree of acetylation of chitosan and distribution of acetyl groups . . . . . . . . . . . . . . . . . . . . . 612
Tel.: +33 476037627; fax: +33 476547203.
E-mail address: marguerite.rinaudo@cermav.cnrs.fr.
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doi: 10.1016/j.progpolymsci.2006.06.001
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3.1.3.
Molecular weight of chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 614
3.1.4.
Persistence length of chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 616
3.2.
Complex formation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617
3.2.1.
Complex formation with metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 617
3.2.2.
Electrostatic complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 618
3.3.
Chitosan-based materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
3.4.
Chemical modification of chitosan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
3.4.1.
Modification reactions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
3.4.2.
Some chitosan derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 620
3.5.
Applications of chitosan and chitosan derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 622
4.
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 624
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 625
General references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 632
1. Introduction
Chitin, poly ( b -(1 4)N -acetyl-
D
-glucosamine), is a natural polysaccharide of major importance, first identified in 1884 (
synthesized by an enormous number of living organisms; and considering the amount of chitin produced annually in the world, it is the most abundant polymer after cellulose. Chitin occurs in nature as ordered crystalline microfibrils forming structural components in the exoskeleton of arthropods or in the cell walls of fungi and yeast. It is also produced by a number of other living organisms in the lower plant and animal kingdoms, serving in many functions where reinforcement and strength are required.
Fig. 1. Chemical structure (a) of chitin poly( N -acetylb -
D
glucosamine) and (b) of chitosan (poly(
D
-glucosamine) repeat units. (c) Structure of partially acetylated chitosan, a copolymer characterized by its average degree of acetylation DA.
Despite the widespread occurrence of chitin, up to now the main commercial sources of chitin have been crab and shrimp shells. In industrial processing, chitin is extracted from crustaceans by acid treatment to dissolve calcium carbonate followed by alkaline extraction to solubilize proteins. In addition a decolorization step is often added to remove leftover pigments and obtain a colorless product. These treatments must be adapted to each chitin source, owing to differences in the ultrastructure of the initial materials (the extraction and pre-treatment of chitin are not described in this paper). The resulting chitin needs to be graded in terms of purity and color since residual protein and pigment can cause problems for further utilization, especially for biomedical products. By partial deacetylation under alkaline conditions, one obtains chitosan, which is the most important chitin derivative in terms of applications.
This review aims to present state-of-the-art knowledge of the morphology of chitin and chitosan and to indicate the best methods for characterization in solution or solid state. The last decade of development will be discussed, as well as recent chemical modifications solution the uses of chitin to be expanded.
2. Chitin
2.1. Chitin structure in the solid state
Depending on its source, chitin occurs as two allomorphs, namely the a and b forms
can be differentiated by infrared and solid-state
NMR spectroscopy together with X-ray diffraction.
A third allomorph g -chitin has also been described
, but from a detailed analysis, it seems that it is
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 just a variant of the a family
.
a -Chitin is by far the most abundant; it occurs in fungal and yeast cell walls, in krill, in lobster and crab tendons and shells, and in shrimp shells, as well as in insect cuticle. It is also found in or produced by various marine living organisms. In this respect, one can cite the harpoons of cone snails
, the oral grasping spine of Sagitta
and the filaments ejected by the seaweed
Phaeocystis
etc. These exotic a -chitins have proved particularly interesting for structural studies since, in comparison with the abundant arthropod chitin, some of them present remarkably high crystallinity
together with high purity (they are synthesized in the absence of pigment, protein, or calcite). In addition to the native chitin, a -chitin systematically results from recrystallization from solution
[11,12] , in vitro biosynthesis [13,14]
or enzymatic polymerization
The rarer b -chitin is found in association with proteins in squid pens
and in the tubes synthesized by pogonophoran and vestimetiferan worms
. It occurs also in aphrodite chaetae
as well as in the lorica built by some seaweeds or protozoa
[19,20] . A particularly pure form of
b -chitin is found in the monocrystalline spines excreted by the diatom Thalassiosira fluviatilis
[20–22] . As of today, it has not been possible to
obtain b -chitin either from solution or by in vitro biosynthesis.
2.1.1. Crystallography of chitin
The crystallography of chitin has been investigated for a long time
[23–26] . Examples of diffrac-
tion diagrams are shown in
glance the powder X-ray diagrams of chitins from shrimp shell ( a -chitin) and anhydrous squid pen ( b chitin) appear nearly the same, but in a refined analysis, they can be differentiated in two ways: (i) a
Fig. 2. X-ray powder diffraction diagrams (a) of a -chitin from purified shrimp cuticle and (b) of b -chitin from dried purified squid pen.
605
Fig. 3. Electron diffraction patterns of highly crystalline chitin:
(a) b * c * projection of a -chitin recorded from a fragment of grasping spine of the arrow worm Sagitta ; (b) b * c * projection of dried b -chitin recorded from a microfibril from the tube of the vestimentiferan worm Tevnia jerichonana .
strong diffraction ring, often quoted as the a -chitin signature is found at 0.338 nm (
) whereas a similar ring occurs at 0.324 nm in b -chitin; (ii) an inner ring at 0.918 nm in b -chitin is sensitive to hydration, moving to 1.16 nm in the presence of liquid water, whereas a similar strong inner ring at
0.943 nm in a -chitin is insensitive to hydration.
Further information on the crystalline structure of a - and b -chitin is obtained by analysis of electron diffraction patterns of highly crystalline samples.
Examples are shown in
a is taken on a fragment of a Sagitta grasping spine and 3 b on a microfibril extracted from a tube synthesized by a vestimentiferan worm Tevnia jerichonana . These two patterns, corresponding to b * c * projections, indicate clearly that along the b * direction, the cell parameter of a -chitin is close to twice that of b -chitin, whereas the c * parameter is the same in both patterns. In addition the a * c * projections (not shown) of a - and b -chitin are nearly identical in both allomorphs. These observations are consistent with the currently accepted crystalline parameters and symmetry elements of a - chitin and anhydrous b -chitin (
Table 1 ). The crystallographic parameters
of a and b -chitin reveal that there are two antiparallel molecules per unit cell in a -chitin, whereas only one is present in b -chitin, which consists therefore of a parallel arrangement. Despite this difference, it appears that the N -acetyl glycosyl moiety is the independent crystallographic unit in both allomorphs.
The proposed crystal structures of a - and b -chitin are represented in
. In both structures, the chitin chains are organized in sheets where they are tightly held by a number of intra-sheet hydrogen bonds. This tight network, dominated by the rather strong C–O
?
NH hydrogen bonds, maintains the
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
Table 1
Crystallographic parameters of a - and b -chitins a (nm) a -Chitin anhydrous b -chitin
0.474
0.485
b (nm)
1.886
0.926
c (nm)
1.032
1.038
g (
1
)
90
97.5
Space group
P2
1
2
1
2
1
P2
1
Ref.
Fig. 4. Structure of a -chitin: (a) ac projection; (b) bc projection;
(c) ab projection. The structure contains a statistical mixture of 2 conformations of the –CH
2
OH groups
.
chains at a distance of about 0.47 nm (
) along the a parameter of the unit cell. In a -chitin, there are also some inter-sheet hydrogen bonds along the b parameter of the unit cell, involving association of the hydroxymethyl groups of adjacent chains. Such a feature is not found in the structure of b -chitin, which is therefore more susceptible than a -chitin to intra-crystalline swelling. The current model for the crystalline structure of a -chitin indicates that the inter-sheet hydrogen bonds are distributed in two sets (
occupancy in each set
. It is not clear whether this feature is general for all a -chitin samples or specific to lobster tendon chitin, which was used in the structure determination. In this respect, the observation of diffraction patterns of various a -chitin samples indicates some discrepancy in their diffraction patterns. In particular the X-ray pattern of lobster tendon chitin presents a marked 001 diffraction spot
[26] , which is absent in the more
crystalline Sagitta chitin
. Therefore, it
Fig. 5. Structure of anhydrous b -chitin: (a ) ac projection; ( b) bc projection; (c) ab projection. The set of coordinates defined in
Ref.
could not be used due to an error in the definition of the
N -acetyl moiety. Instead coordinates provided by Y. Noishiki, Y.
Nishiyama and M. Wada in a private communication were used to draw the molecular structure of b -chitin.
appears that more work is required to resolve these ambiguities about the crystal structure of a -chitin.
In contrast, the structure of anhydrous b -chitin appears to be well established. However, the crystal structure of the b -chitin hydrate remains to be refined, as some uncertainty exists, even as to its unit cell parameters
.
2.1.2. Reversible and irreversible intra-crystalline swelling of chitin
As mentioned above, no inter-sheet hydrogen bond is found in the crystal structure of b -chitin, whereas the sheets themselves are tightly bound by a number of intra-sheet hydrogen bonds. This remarkable feature explains why a number of polar guest molecules, ranging from water to alcohol and amines, can readily penetrate the crystal lattice of b -chitin without disturbing the sheet organization
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 and the crystallinity of the samples. This swelling is quite rapid: it was found that the highly crystalline chitin from pogonophore tubes could be swollen in water in about a minute
penetrated the crystalline lattice of b -chitin, it can be displaced by another one of a different chemical family to produce a wide distribution of crystalline b -chitin complexes. Essentially, during swelling the b parameters of the b -chitin unit cell expand laterally whereas a and c remain constant. The incorporation of the swelling agent within the crystalline lattice is thus indicated by the position of the 010 diffraction spot.
lists the variation of the position of this spot with respect to a selection of representative guests. This intracrystalline swelling is reversible, as in all these cases removal of the guest molecule allows the structure to revert to its original state of anhydrous b -chitin, though with some loss of crystallinity.
The inter-sheet swelling of a -chitin crystals is more specific. Whereas water and alcohols cannot penetrate the crystalline lattice of a -chitin, stronger swelling agents such as aliphatic diamines have been shown to intercalate into the crystalline lattice to form highly crystalline complexes
b -chitin, the guest molecules are incorporated between the chitin sheets of a -chitin and accordingly, the b cell parameter expands, whereas the a and c parameters remain essentially constant. The inter-sheet parameter expansion, which is about the same in both a - and b -chitin, increases linearly with
Table 2
Variation of the 010 diffraction spot of b -chitin with incorporation of various guest molecules
Guest Position of the 010 diffraction spot
Ref.
(nm)
No guest
Water
Methanol n -butanol n -octanol n -hexylamine
Ethylenediamine
(type I)
Ethylenediamine
(type II)
Acrylamide p -aminobenzoic acid
D-glucose
0.917
1.16
1.30
1.55
1.97
1.81
1.18
1.45
1.33
1.31
1.27
a
a
This value corresponds to b -chitin dihydrate. Under reduced hydration conditions the b -chitin monohydrate is obtained, for which the 010 diffraction spot is at 1.04 nm
.
607 the number of carbon atoms in a diamine guest: an expansion of 0.7 nm being observed, for instance, in the case of the C7 diamine
.
Whereas the intra-crystalline swelling of b -chitin in water, alcohols or amines is reversible, its swelling in relatively strong acid media, namely concentrated nitric acid or 6–8 M HCl, leads irreversibly a -chitin
[18,33] . During this swelling, not only the inter-
sheet, but also the intra-sheet hydrogen bonds are broken
and the crystalline state appears to be completely lost
. Nevertheless the crystallinity is restored, as a -form crystals, upon removal of the acid. In the case of oriented material, such as squid pen chitin, the b a conversion is also marked by a substantial shrinkage of the structure
. To account for this shrinkage and the solid-state b a conversion, a chain folding mechanism has tentatively been proposed
. Other possibilities involving the interdigitation of b -chitin microfibrils of opposite polarities can also be envisaged. At the ultrastructural level, it was found that substantial hydrolysis followed by partial dissolution occurred during the acid treatment. When a subsequent washing step was applied, the shortest hydrolyzed chains were found to recrystallize by epitaxy on the underlying unhydrolyzed chitin chains, leading to a shish-kebab morphology
. Thus, the conversion did not occur at a single crystal level, but some or all b -chitin crystals were destroyed during the acid swelling and new crystals of a -chitin were produced during recrystallization. The irreversibility of the b a conversion indicates that a -chitin is thermodynamically more stable than b -chitin. This stability is confirmed by the fact that a -chitin is always obtained in recrystallization from solution.
2.1.3. Infrared spectroscopy of chitin
A number of studies have dealt with the description and interpretation of the infrared spectra of chitin
a - and b -chitin samples shown in
are typical of polysaccharides; because of the high crystallinity of the samples, they display a series of very sharp absorption bands. The
C
Q
O stretching region of the amide moiety, between 1600 and 1500 cm
1
, is quite interesting as it yields different signatures for a -chitin and b -chitin. For a -chitin, the amide I band is split at
1656 and 1621 cm
1626 cm
1 for b
1
, whereas it is unique, at
-chitin. In contrast, the amide II band is unique in both chitin allomorphs: at
1556 cm
1 for a -chitin and 1560 cm
1 for b -chitin.
The occurrence of two amide I bands for a -chitin
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 its inter-sheet hydrogen bonding does not allow us to give a definitive explanation for this band.
2.1.4.
13
C CP-MAS solid state spectroscopy
A number of
13
C solid-state NMR spectra of a - and b -chitin have been published
, the most crystalline samples yielding the best resolved spectra. Examples of such spectra are shown in
, and a list of their corresponding chemical shifts is presented in
. When recorded at
7.05 T, each spectrum consists of 6 single-line signals and 2 doublets at C-2 and C
Q
O, but these doublets are in fact singlets that are split by the effect of the
14
N quadrupole coupling
splitting disappears if the spectra are acquired at higher field strength and, on the other hand, becomes broader at lower field strength. In accounting for this phenomenon, there are therefore only 8 signals for the 8 carbon atoms of a - and b -chitins.
Thus, in both allomorphs, the N -acetyl
D
-glucosamine moiety can be considered as the magnetic independent residue, in full agreement with the crystal structure of a - and b -chitin where this residue is also the crystallographic independent unit. In looking at the data in
the spectra of a - and b -chitin are nearly the same, and it is not easy to differentiate them by solid-state
13
C NMR. Nevertheless, the relaxation time of C-6
Fig. 6. FTIR spectra of chitin: (a) for single crystals of a -chitin;
(b) for deproteinized dried b -chitin from the tube of Tevnia jerichonana .
has been the subject of debate. The band at
1656 cm
1
, which occurs at similar wavelengths in polyamides and proteins, is commonly assigned to stretching of the C
Q
O group hydrogen bonded to
N–H of the neighboring intra-sheet chain. Regarding the 1621 cm
1 band , which is not present in polyamides and proteins, its occurrence may indicate a specific hydrogen bond of C
Q
O with the hydroxymethyl group of the next chitin residue of the same chain
. This hypothesis is reinforced by the presence of only one band in this region for N acetyl
D
-glucosamine
. Also, in a -chitin, the band at 1621 cm
1 is modified in deuterated water, whereas the band at 1656 cm
1 remains nearly unaffected
[40] . Other possibilities may also be
considered, as the band at 1621 cm
1 could be either a combination band or due to an enol form of the amide moiety
[37] . The lack of a more precise
definition of the molecular structure of a -chitin and
Fig. 7.
13
C CP/MAS solid state spectra of (a) a -chitin from deproteinized lobster tendon; (b) b -chitin from dried deproteinized tube of Tevnia jerichonana . Reprinted with permission from
Macromolecules 1990; 23: 3576–3583. Copyright 2006, American
Chemical Society.
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
Table 3
Chemical shifts of solid chitin
Anhydrous b -chitin from diatom spines
(ppm) a -chitin from lobster tendon (ppm)
C1
C2
C3
C4
C5
C6 a
C
Q
O a
105.4
55.3
73.l
73.1
84.5
75.5
59.9
175.6
176.4
22.8
104.6
55.6
73.7
83.6
61.1
173.0
CH
3
23.1
Reprinted with permission from Macromolecules 1990; 23:
3576–3583. Copyright 2006, American Chemical Society.
a
The splitting for C-2 and C
Q
O is due to the
14
N quadrupole coupling.
in crab shell a -chitin is found to be much shorter than that of the other carbons of this chitin and also shorter than for C-6 of anhydrous b -chitin
.
A possible explanation may be related to the specificity of the split hydrogen bonds linking the hydroxymethyl groups of the a -chitin molecules from adjacent sheets. A refinement of the crystalline and molecular structure of a -chitin should help in understanding not only this hydrogen bonding situation but should also give a clue for the short relaxation time of C-6. It also remains to be seen whether this fast relaxation is specific for crab shell chitin or is general for all crystalline a -chitins.
2.2. Solubility of chitin and chain characterization
Chitin occurs naturally partially deacetylated
(with a low content of glucosamine units), depend-
)
a and b forms are insoluble in all the usual solvents, despite natural variations in crystallinity. The insolubility is a major problem that confronts the development of processing and uses of chitin. An important mechanism previously mentioned is that a solid-state transformation of b -chitin into a -chitin occurs by treatment with strong aqueous HCl (over
7 M) and washing with water
. In addition, b -chitin is more reactive than the a form, an important property in regard to enzymatic and chemical transformations of chitin
.
Because of the solubility problem, only limited information is available on the physical properties of chitin in solution. The first well-developed study
609
Table 4
Sources of chitin and chitosan
Sea animals Insects Microorganisms
Annelida
Mollusca
Coelenterata
Crustaceans:
Lobster
Crab
Shrimp
Prawn
Krill
Scorpions
Spiders
Brachiopods
Ants
Cockroaches
Beetles
Green algae
Yeast ( b -type)
Fungi (cell walls)
Mycelia Penicillium
Brown algae
Spores
Chytridiaceae
Ascomydes
Blastocladiaceae
Reprinted with permission from J Chem Educ 1990; 67: 938–942.
Used with permission from the Journal of Chemical Education, vol. 6, No. 11, 1990, pp. 938–942; copyright r 1990, Division of
Chemical Education, inc.
was by Austin
[48] , who introduced the solubility
parameters for chitin in various solvents. He obtained a complex between chitin and LiCl (which is coordinated with the acetyl carbonyl group). The complex is soluble in dimethylacetamide and in
N -methyl-2-pyrrolidone. We recall that the same solvents and, especially, LiCl/DMAc mixtures, are also solvents for cellulose, another b (1
-
4) glucan
[49] . In addition, Austin also used formic, dichlor-
oacetic and trichloroacetic acids for dissolution of chitin chains.
Experimental values of parameters K and a relating intrinsic viscosity [ Z ] and molecular weight
M for chitin in several solvents according to the well-known Mark–Houwink equation
½ Z ¼ KM a
(1) are given in
. Molecular weights were determined by light scattering using the d n /d c values mentioned in the table.
For a long time the most widely used solvent for chitin was a DMAc/LiCl mixture, though CaCl
2
2H
2
O-saturated methanol was also employed, as well as hexafluoroisopropyl alcohol and hexafluoracetone sesquihydrate
. Vincendon
dissolved chitin in concentrated phosphoric acid at room temperature. In this solvent, decreases of the viscosity and of the molar mass were observed with time with no change in the degree of acetylation.
The same author also dissolved chitin in a fresh saturated solution of lithium thiocyanate and got the NMR spectra at 90
1
C
. A few papers discuss preparation of alkali chitin by dissolution of chitin at low temperature in NaOH solution. The chitin is first dispersed in concentrated NaOH and allowed
610
Table 5
Mark–Houwink parameters of chitin
Solvent K (mL/g)
2.77 M NaOH
DMAc/LiCl 5%
DMAc/LiCl 5%
0.1
7.6
10
2.4
10
3
1
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 a
0.68
0.95
0.69
T (
1
C)
20
30
25 d n /d c
0.145
0.091
0.1
Ref.
to stand at 25
1
C for 3 h or more; the alkali chitin obtained is dissolved in crushed ice around 0 1 C. This procedure allowed the authors to cast transparent chitin film with good mechanical properties
. The resulting chitin is amorphous and, under some conditions, it can be dissolved in water, while chitosan with a lower degree of acetylation (DA) and ordinary chitin are insoluble. The authors interpreted this phenomenon as related both to the decrease of molecular weight under alkaline conditions and to some deacetylation; they confirmed that to get water solubility, the DA has to be around 50% and, probably, that the acetyl groups must be regularly dispersed along the chain to prevent packing of chains resulting from the disruption of the secondary structure in the strong alkaline medium
.
Recently, an interesting study, utilizing techniques such as rheology, turbidimetry and fluorescence, demonstrated that alkali chitin solubilized in cold
( 0
1
C) aqueous NaOH (16% w/w) according with the protocol of Sannan et al.
forms an LCST solution with a critical temperature around 30
1
C
.
A chitin gel, obtained from the solution by washing to extract NaOH, was found to be temperature and pH-sensitive
[59] . These authors demonstrated a
volume phase transition at 21
1
C as the result of the influence of temperature on polymer–polymer and polymer–water interactions such as hydrogen bonding and hydrophobic interactions. This transition is observed only within a narrow range of pH (7.3–7.6) and modifies the mechanical shear modulus as a function of oscillating variation in temperature.
The rheology of chitin in solution is that of a semi-rigid polysaccharide for which the conformational analysis has been developed in comparison with chitosan; this point will be taken up later in the discussion of the role of the DA on the intrinsic persistence length of the polymer.
2.3. Chitin derivatives
The most important derivative of chitin is
chitosan ( Fig. 1 ), obtained by (partial) deacetylation
of chitin in the solid state under alkaline conditions
(concentrated NaOH) or by enzymatic hydrolysis in the presence of a chitin deacetylase. Because of the semicrystalline morphology of chitin, chitosans obtained by a solid-state reaction have a heterogeneous distribution of acetyl groups along the chains. In addition, it has been demonstrated that b -chitin exhibits much higher reactivity in deacetylation than a -chitin
distribution was examined by Aiba
, who showed that the distribution, random or blockwise, is very important in controlling solution properties.
Reacetylation, up to 51%, of a highly deacetylated chitin in the presence of acetic anhydride gives a water soluble derivative, whereas a heterogeneous product obtained by partial deacetylation of chitin is soluble only under acidic conditions, or even insoluble. It was demonstrated from NMR measurements that the distribution of acetyl groups must be random to achieve the higher water solubility around 50% acetylation.
Homogeneously deacetylated samples were obtained recently by alkaline treatment of chitin under dissolved conditions
reacetylation of a highly deacetylated chitin was done by Maghami and Roberts
, incidentally providing homogeneous samples for our SEC analysis discussed below. Toffey et al. transformed chitosan films cast from aqueous acetic acid into chitin by heat treatment
most studied derivative of chitin is carboxymethylchitin (CM-chitin), a water-soluble anionic polymer.
The carboxymethylation of chitin is done similarly to that of cellulose; chitin is treated with monochloracetic acid in the presence of concentrated sodium hydroxide. The same method can be used for carboxymethylation of chitosan
. The method for cellulose derivatization is also used to prepare hydroxypropylchitin, a water-soluble derivative used for artificial lachrymal drops
Other derivatives such as fluorinated chitin
N and O -sulfated chitin
, (diethylamino)ethylchitin
, phosphoryl chitin
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 and chitin carbamates
have been described in the literature. Modification of chitin is also often effected via water soluble derivatives of chitin (mainly CMchitin). The same type of chemical modifications
(etherification and esterification) as for cellulose can be performed on the available C-6 and C-3 –OH groups of chitin
.
Chitin can be used in blends with natural or synthetic polymers; it can be crosslinked by the agents used for cellulose (epichlorhydrin, glutaraldehyde, etc.) or grafted in the presence of ceric salt
or after selective modification
Chitin is partially degraded by acid to obtain series of oligochitins
well as those derived from chitosan, are recognized for their bioactivity: including anti-tumor, bactericidal and fungicidal activity, eliciting chitinase and regulating plant growth. They are used in testing for lysozyme activity. They are also used as active starting blocks to be grafted on protein and lipids to obtain analogs of glycoproteins and glycolipids.
2.4. Applications of chitin
Chitin has low toxicity and is inert in the gastrointestinal tract of mammals; it is biodegradable, owing to the presence of chitinases widely distributed in nature and found in bacteria, fungi and plants, and in the digestive systems of many animals. Chitinases are involved in host defense against bacterial invasion. Lysozymes from egg white, and from fig and papaya plants, degrade chitin and bacterial cell walls. Sashiva et al.
showed that a certain degree of deacetylation is necessary to allow hydrolysis of chitin
Chitin has been used to prepare affinity chromatography column to isolate lectins and determine their structure
O -carboxymethylchitin activate peritoneal macrophages in vivo, suppress the growth of tumor cells in mice, and stimulate nonspecific host resistance against Escherichia Coli infection. Chitin also accelerates woundhealing
Chitin is widely used to immobilize enzymes and whole cells; enzyme immobilization has applications in the food industry, such as clarification of fruit juices and processing of milk when a - and b -amylases or invertase are grafted on chitin
On account of its biodegradability, nontoxicity, physiological inertness, antibacterial properties, hydrophilicity, gel-forming properties and affinity
611 for proteins, chitin has found applications in many areas other than food such as in biosensors
Chitin-based materials are also used for the treatment of industrial pollutants and adsorbs silver thiosulfate complexes
and actinides
.
Chitin can be processed in the form of films and fibers: fibers were first developed by Austin
and then by Hirano
. The chitin fibers, obtained by wet-spinning of chitin dissolved in a 14% NaOH solution, can also result of blending with cellulose
or silk
[86] . They are nonallergic, deodorizing,
antibacterial and moisture controlling
. Regenerated chitin derivative fibers are used as binders in the paper making process; addition of 10% n -isobutylchitin fiber improves the breaking strength of paper
However, the main development of chitin film and fiber is in medical and pharmaceutical applications as wound-dressing material
and controlled drug release
[90,91] . Chitin is also used as an
excipient and drug carrier in film, gel or powder form for applications involving mucoadhesivity.
Another interesting application is in a hydroxyapatite–chitin–chitosan composite bone-filling material, which forms a self-hardening paste for guided tissue regeneration in treatment of periodontal bony defects
Chitin was also O -acetylated to prepare gels which are still hydrolyzed by enzyme such as henegg white lysozyme
. CM-chitin was selectively modified to obtain antitumor drug conjugates
For example, 5-fluorouracil which has marked antitumor activity and the
D
-glucose analog of muramylL -alanyl-isoglutamine, responsible for immuno-adjuvant activity were grafted on CM-chitin using a specific spacer and an ester bond.
Chitin oligomers have been claimed as anticancer drugs, and the oligomer with DP ¼ 5 is active in controlling the photosynthesis of maize and soybeans
.
3. Chitosan
When the degree of deacetylation of chitin reaches about 50% (depending on the origin of the polymer), it becomes soluble in aqueous acidic media and is called chitosan. The solubilization occurs by protonation of the –NH
2 function on the
C-2 position of the
D
-glucosamine repeat unit, whereby the polysaccharide is converted to a polyelectrolyte in acidic media. Chitosan is the only pseudonatural cationic polymer and thus, it finds
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 many applications that follow from its unique character (flocculants for protein recovery, depollution, etc.). Being soluble in aqueous solutions, it is largely used in different applications as solutions, gels, or films and fibers. The first step in characterizing chitosan is to purify the sample: it is dissolved in excess acid and filtered on porous membranes
(with different pore diameters down to 0.45
m m).
Adjusting the pH of the solution to ca. 7.5 by adding NaOH or NH
4
OH causes flocculation due to deprotonation and the insolubility of the polymer at neutral pH. The polymer is then washed with water and dried.
3.1. Chitosan structure and characterization
In the solid state, chitosan is a semicrystalline polymer. Its morphology has been investigated, and many polymorphs are mentioned in the literature.
Single crystals of chitosan were obtained using fully deacetylated chitin of low molecular weight
.
The electron diffraction diagram can be indexed in an orthorhombic unit cell (P2
1
2
1
2
1
) with a ¼ 0 : 807 nm, b ¼ 0 : 844 nm, c ¼ 1 : 034 nm; the unit cell contains two antiparallel chitosan chains, but no water molecules. The influence of experimental conditions on the crystallinity has also been described
The main investigations of chitosan concern its preparation with varied molecular weights and DA from chitin, the dependence of its solution properties on the DA, the preparation of derivatives and applications. Sponges, powders and fibers can be obtained by regeneration of chitosan or its derivatives from solutions. These points will be developed in the following discussion.
3.1.1. Solubility of chitosan
A highly deacetylated polymer has been used to explore methods of characterization
. The solution properties of a chitosan depend not only on its average DA but also on the distribution of the acetyl groups along the main chain in addition of the molecular weight
[57,60,100] . The deacetylation,
usually done in the solid state, gives an irregular structure due the semicrystalline character of the initial polymer. Examination of the role of the protonation of chitosan in the presence of acetic acid
and hydrochloric acid on solubility
showed that the degree of ionization depends on the pH and the p K of the acid. Solubilization of chitosan with a low DA occurs for an average degree of ionization a of chitosan around 0.5; in
HCl, a ¼ 0 : 5 corresponds to a pH of 4.5–5.
Solubility also depends on the ionic concentration, and a salting-out effect was observed in excess of
HCl (1 M HCl), making it possible to prepare the chlorhydrate form of chitosan. When the chlorhydrate and acetate forms of chitosan are isolated, they are directly soluble in water giving an acidic solution with p K
0
¼ 6
7
0.1
, in agreement with previous data
and corresponding to the extrapolation of p K for a degree of protonation a ¼ 0. Thus, chitosan is soluble at pH below 6.
The solubility of chitosan is usually tested in acetic acid by dissolving it in 1% or 0.1 M acetic acid. We demonstrated that the amount of acid needed depends on the quantity of chitosan to be dissolved
[101] . The concentration of protons
needed is at least equal to the concentration of
NH
2 units involved.
In fact, the solubility is a very difficult parameter to control: it is related to the DA, the ionic concentration, the pH, the nature of the acid used for protonation, and the distribution of acetyl groups along the chain, as well as the conditions of isolation and drying of the polysaccharide. It is important also to consider the intra-chain H bonds involving the hydroxyl groups as shown below. The role of the microstructure of the polymer is clearly shown when a fully deacetylated chitin is reacetylated in solution; the critical value of chitosan DA to achieve insolubility in acidic media is then greater than 60%. In addition, solubility at neutral pH has also been claimed for chitosan with DA around
50%
.
Recently, a water-soluble form of chitosan at neutral pH was obtained in the presence of glycerol
2-phosphate
. Stable solutions were obtained at pH 7–7.1 and room temperature, but a gel formed on heating to about 40
1
C. The sol–gel transition was partially reversible and the gelation temperature depended slightly upon experimental
).
3.1.2. Degree of acetylation of chitosan and distribution of acetyl groups
The characterization of a chitosan sample requires the determination of its average DA. Various techniques, in addition to potentiometric titration
[108] , have been proposed, such as IR
, elemental analysis, an enzymatic reaction
, UV
1
H liquid-state NMR
and solid-state
13
C
NMR
[115–117] . The fraction of –NH
2 in the
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 613
1000
100.0
10.00
1000
100.0
10.00
1.000
10.0
20.0
30.0
40.0
temperature(˚C)
50.0
60.0
70.0
1.000
Fig. 8. Dynamic rheology giving the moduli G 0 and G 00 at 1 Hz frequency as a function of temperature for a chitosan-glycerol-phosphate solution: evidence of thermogelation at pH ¼ 7.19. Polymer concentration 15 g/L. Heating curves: storage modulus G 0 ( & ), loss modulus
G 00 ( ’ ). Cooling curves: G 0 , ( , ), G 00 ( .
).
1000 1000
100.0
10.00
100.0
10.00
1.000
1.000
0.1000
0.01000
0.1000
1.000
frequency (Hz)
0.1000
10.00
Fig. 9. Dynamic rheological moduli for chitosan-glycerol 2-phosphate at pH ¼ 7.19 at two different temperatures. Polymer concentration
15 g/L. (a) 10
1
C: G 0 ( J ), G 00 ( K ) indicate a viscoelastic behaviour. (b) 70
1
C: G 0 ( B ), G 00 ( E ) indicate a gel-like behaviour.
polymer (which determines the DA) can be obtained by dissolution of neutral chitosan in the presence of a small excess of HCl on the basis of stoichiometry followed by neutralization of the protonated –NH
2 groups by NaOH using pH or conductivity measurements. These techniques and the analysis of the data obtained have been previously described
.
Presently, we consider that
1
H NMR is the most convenient technique for measuring the acetyl content of soluble samples.
gives the
1
H spectrum obtained for chitosan dissolved in D
2
O containing DCl (pD ca. 4).The signal at 1.95 ppm allows determination of the acetyl content by reference to the H-1 signal at 4.79 ppm for the
D
-glucosamine residue and at 4. 50 ppm for the H-1 of the N -acetyl-
D
-glucosamine unit at 85 1 C.
15
13
C and
N solid state NMR were also tried and discussed recently; these techniques were used over the whole range of acetyl content from 0% to 100%. As an example, the chemical shifts for carbon atoms on 4 samples are given in
a -chitin, B is a homogeneous reacetylated chitosan and C, D are commercial samples
.
15
N NMR gives only two signals related to the amino group and to the
N
-acetylated group ( Fig. 11 ); this technique can be
used in the solid state, whatever the DA.
13
C was
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
Fig. 10.
1
H NMR spectrum of chitosan in D
2
O, pH 4,
T ¼ 85
1
C, conc. 5 g/L: (1) H-1 of glucosamine units, (2) H-1 of
N -acetyl-glucosamine, (3) H-2, (4) protons of the acetyl group of
N -acetyl-glucosamine.
Fig. 11.
15
N CP-MAS NMR spectra of (A) a -chitin, (B) homogeneous partially reacetylated chitosan, (C and D) heterogeneous commercial chitosans. Reprinted with permission from
Biomacromolecules 2000; 1:746–751.Copyright 2006, American
Chemical Society.
Table 6
Chemical shifts of chitin and chitosan obtained by
13
CP-MAS.
(A) a -chitin, (B) chitosan obtained by partial reacetylation, (C and D) commercial chitosans
Samples
C
Q
O
C1
C4
C5
C3
C6
C2
CH
3
A
173.8
104.1
83.0
75.7
73.3
60.8
55.2
22.8
B
173.7
103.5
82.4
74.7
74.7
60.3
56.6
23.1
C
173.6
104.7
82.4
75.0
75.0
60.1
57.6
23.2
D nd
104.7
85.7–81.0
74.1
74.1
60.7–59.6
56.8
nd
Reprinted with permission from Biomacromolecules
2000;1:746–751. Copyright 2006, American Chemical Society.
also compared with
1
H NMR and
15
N NMR and good agreement was found over the entire range of
DA, whatever the state of the sample ( Table 7
).
The distribution of acetyl groups along the chain
(random or blockwise) may influence the solubility of the polymer and also the inter-chain interactions due to H-bonds and the hydrophobic character of the acetyl group. This distribution was evaluated from
13
C NMR measurements
; diad and triad frequencies were determined for homogeneous and heterogeneous chitosan with different values of DA.
3.1.3. Molecular weight of chitosan
Another important characteristic to consider for these polymers is the molecular weight and its
Table 7
Degrees of acetylation of chitin and chitosan obtained by liquid state (
1
H) and solid state (
13
C and
15
N) NMR on the same samples as in
A B C D Samples
DA from
NMR
1
H
(liquid state)
DA from
13
C
NMR
(solid state)
DA from
15
N
NMR
(solid state) insoluble
0.99
1
0.58
0.61
0.63
0.21
0.20
0.20
acetyl traces
0
0
Reprinted with permission from Biomacromolecules 2000; 1:
746–751. Copyright 2006, American Chemical Society.
distribution. The first difficulty encountered in this respect concerns the solubility of the samples and dissociation of aggregates often present in polysaccharide solutions
[120] . As to choice a solvent for
chitosan characterization, various systems have been proposed, including an acid at a given concentration for protonation together with a salt to screen the electrostatic interaction.
The solvent is important also when molecular weight has to be calculated from intrinsic viscosity using the Mark–Houwink relation, Eq. (1) above,
with known values of the parameters K and a.
One solvent first proposed (0.1 M AcOH/0.2 M NaCl) for molecular weight characterization was shown to promote aggregation and to overestimate the values of molecular weights calculated
of the Mark–Houwink parameters for chitosan solutions are given in
. It was demonstrated that the aggregates perturb not only the molecular weight determination by light scattering but also the viscosity determination. To avoid these artifacts, we then proposed to use 0.3 M acetic acid/0.2 M sodium acetate (pH ¼ 4.5) as a solvent since we had no evidence for aggregation in this mixture
[123] . Absolute M values were obtained from size
exclusion chromatography (SEC) with on-line viscometer and light scattering detectors to allow determination of the Mark–Houwink parameters, and also the relation between the molecular radius of gyration R g and molecular weight. This analysis also required determination of the refractive index increment d n /d c (where c is the polymer concentration). More recently, we compared d n /d c values given in the literature with those we determined for samples with various DA values and showed that the DA has a negligible influence on d n /d c in the acetic acid/sodium acetate mixture
tained a value of 0.190 ml/g, which is different from values used by some other authors.
The fractionation by SEC on a preparative scale in
0.02 M acetate buffer/0.1 M NaCl (pH ¼ 4.5) was done and discussed by Berth and Dautzenberg
.
It was applied to chitosans of commercial origin with various DA’s obtained by reacetylation following the protocol of Roberts
[62,121,126] . On the fractions,
static light scattering, using a d n /d c of 0.203 mL/g, and viscosity measurements showed that in the range covered (0.03
o DA o 0.53) the DA had no influence on the properties of the chain. In their paper, the authors also compared their results with all the data previously published in the literature. From this
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 615 comparison, they proposed a set of parameters for the dependence of the intrinsic viscosity [ Z ] and the rms molecular radius of gyration R g weight, valid for all the samples on molecular
½ Z ð mL = g Þ ¼ 0 : 0843 M
0 : 92
(2) and
R g
ð nm Þ ¼ 0 : 075 M
0 : 55
.
(3)
These parameters are in good agreement with the previous results of Rinaudo et al.
the Mark–Houwink parameters with K ¼
0 : 082 mL = g and a ¼ 0 : 76, respectively, when
DA ¼ 2%.
In a more recent paper
, we describe a complete analysis of the molecular weight distribution by SEC using triple detection (viscosity, concentration, molecular weight) on heterogeneous chitosans, obtained from commercial sources after solid-state treatment, and on some homogeneous chitosans with different molecular weights obtained by reacetylation of a highly deacetylated chitosan
[121,126] . The DA of these acid-soluble chitosans
varied from 0.02 to 0.61. The data confirm the conclusion that the stiffness of the chain is nearly independent of the DA and demonstrate that the various parameters depend only slightly on the
DA—a point that will be discussed below in relation to the persistence length.
The relation obtained between R g molecular weight is and the
R g
ð nm Þ ¼ ð 0 : 064 0 : 002 Þ M
0 : 55 0 : 01
.
(4)
We proposed average values for the Mark–Houwink parameters within portions of the total range of DA covered, valid for heterogeneous as well as homogeneous samples (see
relatively high values for the parameter a are in agreement with the semirigid character of this polysaccharide; to validate this conclusion, one
Table 8
Mark–Houwink parameters for chitosan in various solvents
Solvent
0.1 M AcOH/0.2 M NaCl
0.1 M AcOH/0.02 M NaCl
0.2 M AcOH/0.1 M AcONa/4 M urea
0.3 M AcOH/0.2 M AcONa (DA ¼ 0.02)
0.3 M AcOH/0.2 M AcONa (0 o DA o 0.03)
0.02 M acetate buffer/0.1 M NaCl
K (mL/g)
1.81
10
3
3.04
10
3
8.93
10
8.2
10
2
2
7.9
10
2
8.43
10
2 a
0.93
1.26
0.71
0.76
0.796
0.92
T (
1
C)
25
25
25
25
25
25 d n /d c
0.163
0.190
0.203
Ref.
616
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 investigates chitin and chitosan molecular modeling
and compares the predictions with the experimental results obtained by SEC. It is important to mention the usual method of preparing chitosans with various molecular weights using nitrous acid in dilute HCl aqueous solution
We also investigated the influence of the ionic strength on the Mark–Houwink parameters K and a
. The two series of solvents used were
0.3 M acetic acid/variable Na acetate content and
0.02 M acetate buffer (pH ¼ 4.5) buffer with various concentrations of NaCl, allowing to determine the intrinsic viscosity as a function of the salt concentration; from these experimental values, extrapolation to infinite ionic strength is used to approach the y -conditions.
3.1.4. Persistence length of chitosan
The dimensions of chitosan chains and their related hydrodynamic volume and viscometric
Table 9
Mark–Houwink parameters for chitosan with different average
DA in 0.3 M AcOH/0.2 M AcONa
DA (%) K (mL/g) a
0–3
12
22–24
40
56-61
0.079
0.074
0.070
0.063
0.057
0.79
0.80
0.81
0.83
0.825
contribution depend on the semi-rigid character of the polysaccharide chains. Since chitosan in an acid medium is a polyelectrolyte, these properties are influenced by the ion concentration. We have discussed this point, citing static and dynamic light scattering experiments in the dilute and semidilute regimes
[132,133] . The actual persistence length
L t at a given ion concentration contains an intrinsic contribution L p and an electrostatic contribution L e calculated following Odijk’s treatment
. The worm-like model for a semiflexible chain has been developed by several groups and successfully applied to polysaccharides
A conformational analysis of chitins with different degrees of deacetylation was recently developed in our group
. We concluded that chitin and chitosan are semi-rigid polymers characterized by a persistence length (asymptotic value obtained at high degree of polymerization) that depends mod-
erately on the DA of the molecule ( Fig. 12
). From this analysis, chitosan without acetyl groups has an intrinsic persistence length L p
¼ creases as DA increases up to
9 nm at 25
L p
1
C when the electrostatic repulsions are screened.
L p in-
¼ 12 : 5 nm for
DA ¼ 60%, then remains constant up to pure chitin. The local stiffness is related to the conformation of the molecule, and especially to the intra-chain H bond network formed as shown in
. The decrease of the stiffness of chitosan as temperature increases is shown by
1
H NMR
and follows the prediction from molecular
140
120
100
80
60
40
20 chitosan chitin
0
0 200 400 600 800 1000
DP
Fig. 12. Persistence length as a function of the degree of polymerization for chitin and chitosan obtained from molecular modelling at
25
1
C with a dielectric constant D ¼ 80.
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 617 in terms of the destabilization of the local conformation by intra-chain H bonds
The stiffness of the chain plays a large role in the rheological behavior of the molecule but also, even in dilute solution, it affects the existence of interchain H-bonds forming multimers that perturb all characterization of these polysaccharides. The aggregation has been discussed recently and its causes have been analyzed; it seems that H-bonds, as well as hydrophobic attractions, have a role, whatever the DA
Fig. 13. Molecular modelling: (a) of a chitin chain with two H bonds (1) between—OH 3 and O 5, (2) between—OH 6 and O of
C
Q
O; and (b) of a chitosan chain with two H bonds (1) between—OH 3 and O 5, and (2) between—OH 6 and N.
3.2. Complex formation modeling. A critical temperature around 40
1
C is found where L p starts to decrease more rapidly, behavior that is certainly related to the destabilization of H bonds as temperature increases. The difference in L p values between experiment and prediction is not dramatic for chitosan—and it cannot be directly determined for chitin from experiment because of the low solubility of chitin.
It was shown from size exclusion chromatography using three detectors on-line, that L p is about 11 nm, nearly constant, for 0 o
DA o
25%. Up to 60% acetylation, the stiffness of chitosan is not much influenced by the DA, rising only to 15 nm. The influence of the substitution has to be related to the stability of the intra-chain H-bonds, as is shown for chitin and chitosan from molecular modeling (see
Fig. 13 ). The small variation of the persistence length
with DA is in direct relation with the evolution of the
Mark–Houwink parameters in
The persistence length has also been determined by several other authors: it was given as L p
¼
4 : 2 nm for DA ¼ 0.15
from hydrodynamic analysis and the Yamakawa–Fujii approach
,
8 nm
from a combination of SEC experiments and the Odijk treatment
, then 35 nm for chitin and 22 nm for chitosan (DA
E
0.42)
an increase of the chain stiffness as DA increases.
A critical ratio of C
0 o DA o 0.15
C
1
1
¼ 9 was
¼ lim C x
¼ given lim h h
2 i = for xa 2 when the number of sugar units ( x ) goes to infinite;
C x corresponds to the mean-square end-to-end length of the chain normalized by the number x of sugar residues in the chain and a
2
, a being the average length between adjacent glycosidic oxygens.
The decrease of the stiffness of chitosan chain when the DA decreases has been confirmed and analyzed
3.2.1. Complex formation with metals
Chitosan is known to have good complexing ability; the –NH
2 groups on the chain are involved in specific interactions with metals. Many papers are concerned with complexation for the recovery of heavy metals from various waste waters
A mechanism for complex formation with copper at pH 4 5, was proposed
in agreement with
X-ray data on chitosan–copper stretched films
Recently, the mechanism of complex formation with copper in dilute solution was re-examined and two different complexes were proposed, depending on the pH and copper content
. This chelation depends on the physical state of chitosan (powder, gel, fiber, film). Better chelation is obtained for greater degrees of deacetylation of chitin. Thus chelation is related to the –NH
2 the –NH
2 content as well as to distribution
[143] . It is also related to the
DP of oligo-chitosans; the complex starts to form when DP 4 6
. The two forms proposed are:
½
½ Cu ð 2 NH
2
Þ
2 þ ; 2OH ; H
2
O and
Cu ð 2 NH
2
Þ
2
2 þ ; 2OH :
The first complex is formed at pH between 5 and
5.8, while the second forms above pH 5.8; the maximum amount of copper fixed is [Cu]/
[ NH
2
] ¼ 0.5 mol/mol.
The nature of the cation is very important in the mechanism of interaction
chitosan for cations absorbed on film shows selectivity following the order
Cu þ 2 Hg þ 2 4 Zn þ 2 4 Cd þ 2 4 Ni þ 2 4 Co þ 2 Ca þ 2 ;
Eur þ 3 4 Nd þ 3 4 Cr þ 3 Pr þ 3 ; for divalent and trivalent cations (
) used as their chlorides. The effect of the nature of the anion
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
Fig. 14. Ionic selectivity of chitosan: amount (moles) of divalent and trivalent cations fixed per g of film. Reprinted with permission from
Eur Polym J. 2002; 38:1523–1530. Copyright 2006, Elsevier.
was separately demonstrated
: e.g. sulfate increases the fixation on swollen chitosan beads.
In another study chitosan powder was dispersed in silver nitrate solution or used to fill a column to adsorb mercuric ions from a chloride solution
.
It was shown that the conditions for using chitosan
(50 mesh particles of chitosan or chemically crosslinked beads of chitosan) also play a large role in the adsorption and on the kinetics of retention
The complex of chitosan with Fe
3+ was prepared by mixing chitosan powder in 1.5 M ferric chloride; the solid formed was washed, dried and investigated
; these authors obtained an intramolecular water soluble chitosan–Fe(III) complex and determined that one Fe
3+ is coordinated with two chitosan residues, 3 molecules of water and 1 chloride ion. The general fomula given is
½ Fe ð H
2
O Þ
3
ð Glu Þ
2
Cl Cl
2
H
2
O ; where Glu represents the glucosamine moiety. In the complex isolated from an aqueous solution of polymer and ferric chloride mixed in stoichiometric proportions, it is concluded that one Fe
3+ is linked with two –NH
2 groups and 4 moles of oxygen from which at least one water molecule, the remaining N and O being part of the two saccharide units of chitosan (Fe
3+ being hexa or penta coordinated)
. In an X-ray study of chitosan–transition metal complexes, Ogawa et al.
used tendon chitosan immersed in solutions of various salts.
They found the ratio of glucosamine to copper (II) to be 2:1, and the crystal structure of CuCl
2
/ chitosan was different from that in complexes formed with other salts. Derivatives of chitosan have been prepared in efforts to enhance complex formation
. In one study, the same order of ionic selectivity for divalent cations as given above
ments with N was found by calorimetric measure-
-carboxymethylchitosan
3.2.2. Electrostatic complexes
Chitosan, as a polyelectrolyte, is able to form electrostatic complexes under acidic conditions.
Two different types of complexes are considered here: electrostatic complexes with an oppositely charged surfactant (SPEC) and polyelectrolyte complexes (PEC).
3.2.2.1. Complexes with surfactants.
A general behavior of polyelectrolytes is demonstrated with chitosan and sodium dodecyl sulfate (SDS). An electrostatic complex is formed in the presence of a low DA chitosan involving cooperative stacking of surfactant alkyl chains. Apparently the association forms a micellar system that precipitates out, but for very small amounts of added surfactant, interesting interfacial properties are observed. A critical aggregation concentration (c.a.c.) around 100-fold smaller than the c.m.c. of the surfactant alone is detected by surface tension measurements (
)
. The cooperativity of the observed interaction depends directly on the charge density of the chitosan (in fact, it depends on the distance between two adjacent ionic sites), as is shown for carboxymethylchitin in the presence of tetradecyltrimethylammonium bromide (TTAB)
.
In addition, a capsule is formed when a chitosan solution is dropped into a SDS surfactant solution; a chitosan gel layer (characterized by an ordered nanostructure) crosslinked by charged surfactant micelles is formed in the interfacial film
et al.
showed that this structure can encapsulate enzymes.
This type of electrostatic complex has been examined by calorimetry. The strong affinity and
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
Fig. 15. Electrostatic complex formed between chitosan and an anionic surfactant. Surface tension at air–solution interface as a function of the concentration of (1) cationic chitosan (2) anionic surfactant SDS (3) SDS in chitosan ( c ¼ 2 : 7
10
3 monomol = dm
3
) /SDS complex in acetate buffer (0.05 M).
Reprinted with permission from Colloids and surfaces, A:
Physicochem Eng Aspects. 1999; 147: 139–148. Copyright 2006,
Elsevier.
its dependence on the excess of external salt confirm the electrostatic mechanism
This electrostatic interaction has been compared with covalent analogs obtained by grafting alkyl chains on a chitosan backbone (these derivatives will be described below). The interfacial properties of the chitosan-derived polymer surfactant has relatively low surface tension acitivity but interesting bulk properties. The role of sulfated N -acyl chitosan (S–Cn–Chitosan) in a lipid membrane was compared with that of SDS to show that SDS dissociates the membrane, whereas the polymer stabilizes the membrane, and even increases its rigidity, suggesting low toxicity in bioorganisms. In solution, when the alkyl chain in S–Cn–chitosan is longer than 10 units, the polymers form more stable micelles than those formed by the same alkyl chain surfactant alone
Interactions of this kind are relevant to the field of food chemistry, involving specific interactions of chitosans with phospholipids and bile acids
.
3.2.2.2. Complexes with oppositely charged polymers
(proteins, polyanions, DNA).
There are no good examples of polymer/polymer complex formation based on chitosan and neutral polymers, although many electrostatic PEC between chitosan and synthetic or natural polymers are cited in the
619 literature: e.g. polyacrylic acid, sodium salt (PAA), carboxymethylcellulose (CMC)
carrageenan, alginate (extracted from brown algae), pectin, heparin, hyaluronan (HA)
fated cellulose, dextran sulfate, N -acylated chitosan/ chondroitin sulfate
. The electrostatic interaction has been discussed in relation to the stiffness of the backbone and nature of the ionic groups involved. Especially with alginate or HA, a pH-dependent complex is formed, whose stability depends on the ionic strength. The complex formation was investigated in dilute solution by potentiometry following changes in pH and conductivity to determine the fraction of ion pairs (–COO
+
NH
3
–) formed, depending on the experimental conditions
[108,172] . The interaction between chitosan and
alginate gives an electrostatic complex which so far has been used mostly for biological applications.
The complex between DNA and chitosan oligomers
(or polymers) is now under investigation in many laboratories. In a recently published investigation of the mechanism and cooperativity of the complexation with chitosan oligomers
that a minimum DP (and charge) around 6–9 is necessary for stability. The stability of this complex is reduced above pH ¼ 7.4, near the physiological pH, a finding that seems highly relevant for gene delivery applications and is interpreted as one reason for the observed high transfection activity of the oligomer-based complex.
The main applications of these electrostatic complexes are antithrombogenic materials, controlled release systems, encapsulation of drugs, immobilization of enzymes and cells, and gene carriers. Some examples will be discussed below where the applications of alginate/chitosan complexes are discussed.
One aspect of these complexes now in development is the preparation, layer-by-layer (successively, one layer of polyanion–one layer of polycation), of polyelectrolyte capsules or films based on charged biocompatible polysaccharides or chitosan/synthetic PEC
[169,174,175] . In the case of chitosan
capsules
[174] , PAA is used to form the capsules,
then the chitosan is crosslinked and the PAA is redissolved. Such chitosan capsules are more stable than in absence of chemical crosslinking and are pH-sensitive, swelling at low pH and shrinking at high pH. Porous gels (sponges) can be prepared by formation of a calcium alginate gel stabilized by complexation with galactosylated chitosan (a watersoluble derivative)
[176] . A complex in the form of
620
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Na–alginate to a chitosan–CaCl
2 solution. These beads differ from Ca–alginate beads in exhibiting maximum swelling at pH 9
. Oligo-chitosans, low molecular weight chitosans, were also complexed with alginates to form capsules with controlled permeability
3.3. Chitosan-based materials
Chitosan is used to prepare hydrogels, films, fibers or sponges, as previously mentioned, most of the materials are used in the biomedical domain, for which biocompatilibity is essential. Many systems are described in the literature, but we can cite only a few of the most promising. Chitosan is much easier to process than chitin, but the stability of chitosan materials is generally lower, owing to their more hydrophilic character and, especially, pH sensitivity.
To control both their mechanical and chemical properties, various techniques are used, as mentioned previously for chitin. Often, the methods are adapted from the cellulose world.
First, chitosan may be crosslinked by reagents such epichlorohydrin
or 1,
4-butanediol diglycidyl ether
. Specific crosslinking was performed on a blend of starch and chitosan: starch was oxidized to produce a polyaldehyde that reacts with the –NH
2 group of chitosan in the presence of a reducing agent
.
Many chitosan hydrogels are obtained by treatment with multivalent anions: the case of glycerolphosphate is mentioned above
has also been used
as well as tripolyphosphate
.
Blends and composites have been prepared especially by Hirano, in the way mentioned previously for chitin
proposed in the literature: chitosan/polyamide 6
, chitosan/cellulose fibers
lose using a common solvent
polyelthylene glycol
[190] , chitosan/polyvinylpyrro-
lidone and chitosan/polyvinyl alcohol
. Recently, reinforcement of chitosan film with carbon nanotubes was tested; this composite exhibits a large increase of the tensile modulus with incorporation of only 0.8% of multiwalled carbon nanotubes
. The advantage of chitosan in such materials is not only its biodegradability and its antibacterial activity, but also the hydrophilicity introduced by addition of the polar groups able to form secondary interactions (–OH and –NH
2 groups involved in H bonds with other polymers).
The most promising developments at present are in pharmaceutical and biological areas, and at a lower level in cosmetics. This aspect will be described in the following.
3.4. Chemical modification of chitosan
3.4.1. Modification reactions
Among the many mentions of chitosan derivatives in the literature
[65,193,194] , one can differ-
entiate specific reactions involving the –NH
2 group at the C-2 position or nonspecific reactions of –OH groups at the C-3 and C-6 positions (especially esterification and etherification)
2 in the C-2 position is the important point of difference between chitosan and cellulose, where three –OH groups of nearly equal reactivity are available. The main reaction easily performed involving the C-2 position is the quaternization of the amino group or a reaction in which an aldehydic function reacts with –NH
2 by reductive amination. This latter reaction can be performed in aqueous solution under very mild conditions to obtain randomly distributed substituents in a controlled amount along the chitosan chain. This method has been proposed to introduce different functional groups on chitosan using acryl reagents in an aqueous medium; introduction of N -cyanoethyl groups is said to produce some cross-linking through a reaction between the nitrile group and the amine group
. In addition, it is important to note that more regular and reproducible derivatives should be obtained from highly deacetylated chitin
— assuring control of the quality of the initial material that is essential before modification, especially when biological applications are to be explored.
3.4.2. Some chitosan derivatives
3.4.2.1. O-and N-Carboxymethlchitosans.
Carboxymethylchitosan (CM-chitosan) is the most fully explored derivative of chitosan; it is an amphoteric polymer, whose solubility depends on pH. Under controlled reaction conditions (with sodium monochloracetate in the presence of NaOH), one gets O and N -carboxymethylation. The yield of substituents on the three positions was determined by NMR
[196] . This reaction extends the range of pH
(pH 4 7) in which chitosan is water-soluble, but a phase separation due to the balance between positive and negative charges on the polymer was observed at 2.5
o pH o 6.5.
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Most interesting is the preparation of N -carboxymethylchitosan by reaction with glyoxylic acid in the presence of a reducing agent
distribution of monosubstituted (–NH–CH
2
COOH) and disubstituted (–N (–CH
2
COOH)
2
) groups was established by
1
H and
13
C NMR. Disubstitution is easily obtained, giving an interesting derivative for ion complexation. A specific oxidation of the C-6 position hydroxyl group was realized using the
TEMPO reactant on chitin to produce a chitinbased hyaluronic acid analog
. This derivative is water soluble in a wide range of pH, but only if it is prepared from a fully acetylated chitin.
3.4.2.2. Chitosan 6-O-sulfate.
This derivative is an anticoagulant; it was first prepared as an O - sulfated derivative
and more recently as N -sulfated chitosan
.
621 previously
[176] . Carbohydrates can also be intro-
duced without ring opening on the C-6 position
. These derivatives are important as they are recognized by the corresponding specific lectins and thus could be used for drug targeting
A special case is the grafting of a cyclic oligosaccharide, cyclodextrin, discussed below.
3.4.2.6. Chitosan-grafted copolymers.
One of the most explored derivatives is poly(ethylene glycol)grafted chitosan, which has the advantage of being water soluble, depending on the degree of grafting: higher molecular weight PEG at low DS gives higher solubility than low molecular weight PEG
. PEG can be also be introduced by reductive amination of chitosan using PEG-aldehyde
Polypeptides have been grafted by reaction with
N -carboxyanhydrides of amino acids with the purpose of developing new biomaterials
the degree of polymerization of the grafted chains cited in this work remains low (DP ¼ 5.9–6.6).
3.4.2.3. N-methylene phosphonic chitosans.
These interesting anionic derivatives, with some amphoteric character were synthesized under various conditions and proved to have good complexing efficiency for cations such as Ca
2+
, and those of transition metals (Cu (II), Cd (II), Zn (II) etc.)
. The complexation provides corrosion protection for metal surfaces
tives were also modified and grafted with alkyl chains to obtain amphiphilic properties that have potential applications in cosmetics
.
3.4.2.4. Trimethylchitosan ammonium.
This cationic derivative, water soluble over all the practical pH range, is obtained by quaternization of chitosan
with methyl iodide in sodium hydroxide under controlled conditions, and has been fully characterized by NMR
[196c,206] . A large decrease of
molecular weight during this reaction is observed under all conditions tested. These polymers show good flocculating properties with kaolin dispersions, suggesting applications to paper making
Other quaternized derivatives have been prepared are claimed to have antistatic properties
3.4.2.5. Carbohydrate branched chitosans.
Carbohydrates can be grafted on the chitosan backbone at the C-2 position by reductive alkylation: For that purpose, disaccharides (cellobiose, lactose, etc.) having a reducing end group, are introduced, in the presence of a reductant, on chitosan in the openchain form
. These derivatives are water soluble. Galactosylated chitosan was mentioned
3.4.2.7. Alkylated chitosans.
Alkylated chitosans are very important as amphiphilic polymers based on polysaccharides. The first derivative having these characteristics was a C-10-alkyl glycoside branched chitosan with a high degree of substitution
(DS ¼ 1.5), which gelled when heated over 50 1 C
. Another approach was used for selective
N - and O -palmitoylation giving a derivative with two or three long alkyl chains per monomeric unit.
This reaction involved protection and deprotection of the C-6 position
By using carboxylic anhydrides with different chain lengths on CM-chitosan, highly substituted derivatives with low regularity were obtained. They were insoluble in water and their biodegradability was decreased
.
Using the reductive amination, a series of amphiphilic derivatives were produced with different chain lengths ( C n from 3 to 14) and controlled
DS (usually lower than 10% to maintain water solubility in acidic conditions)
was also used to introduce n -lauryl chains
Alkylated chitosans with good solubility in acidic conditions (pH o 6) have a number of very interesting properties. First, they exhibit surface activity and they were compared with corresponding low molecular weight surfactants
same amount of alkyl chains with the same length, they have a relatively low effect on the decrease of the surface tension but they improve much the
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clearly demonstrated that a simple surfactant and modified chitosan have completely different behavior
; secondly, they increase considerably the viscosity of aqueous solution due to hydrophobic inter-chain interactions; especially for C-12 chain length and a DS 5%, a physical gel is obtained ; the formation of this gel depends on the pH
and on salt concentration
gels result from a balance between electrostatic repulsions between the positively charged chitosan chains and hydrophobic attraction due to alkyl chains mainly in relation with their length
hydrophobic domains formed in the systems are important to adsorb hydrophobic molecules such as pyrene (a fluorescent probe used to evidence these domains in dilute solution); these associations can be destroyed reversibly by addition of cyclodextrins which are known to complex the alkyl chains of surfactants
[221,222] . It is interesting to mention
that alkyl chitosans are compatible with neutral and cationic surfactants; it was demonstrated that cationic surfactant adsorbed on the alkyl chain grafted on chitosan, promotes its solubilization
.
This modified chitosan should be adaptable for drug delivery. When these CD-chitosans were mixed with chitosan grafted with adamantane (AD), the specific
recognition led to a self-assembled gel ( Fig. 16
)
[228] . This physical gel is stabilized by specific CD/
AD linkages in a dynamic mechanism with a relaxation time depending on polymer concentration, temperature, and the presence of excess free
CD or AD
3.5. Applications of chitosan and chitosan derivatives
summarizes the main properties of chitosan and potential biomedical and other applications that they imply. The great current interest in medical applications of chitosan and some of its derivatives is readily understood. The cationic character of chitosan is unique: it is the only pseudo-natural cationic polymer. Its film forming properties and biological activity invite new applications.
recalls the main applications of chitosan. The most important fields where the specificity of chitosan must be recognized are cosmetics (especially for hair care in relation to electrostatic interactions) (
maceutical and biomedical applications on which we focus, which probably offer the greatest promise
.
Drug delivery applications include oral, nasal, parenteral and transdermal administration, implants and gene delivery. The transmucosal administration of drugs has been discussed recently
.
3.4.2.8. Cyclodextrin-linked chitosans.
The cyclic oligosaccharides, namely a -, b -, g -cyclodextrins
(CD), are important because of their ability to encapsulate hydrophobic molecules in their toroidal hydrophobic cavity, whose selectivity depends on the number of glucose units (respectively 6, 7,
8
D
-glucose units)
[222–224] . For various applica-
tions, it is interesting to graft the cyclodextrin on a polymeric backbone such as a biocompatible polysaccharide. A synthesis of a - and b -cyclodextrinchitosans with relatively high degree of substitution has been described
. The authors found that these new derivatives had the ability to differentially recognize and retain certain guest compounds based on their molecular shapes and structures. They proposed to use these polymers as supports for reverse-phase adsorption or as adsorbents in controlled release systems.
A b -cyclodextrin with a specific modification on one of the –OH groups on its small side was grafted to chitosan by reductive amination. At a DS lower than 10%, these derivatives are water soluble in acidic conditions with loose inter-chain interactions
[226,227] . The grafted cyclodextrin has the same
association constant as the free CD with small hydrophobic molecules such as adamantane
.
1000
100
10
1
0.1
G', initial chitosan
G'', initial chitosan
G', AD-chit/CD-chit mixture
G'', AD-chit /CD-chit mixture
0.01
0.01
0.1
1
Frequency (Hz)
10
Fig. 16. Rheological behavior ( G 0 and G 00 moduli as a function of frequency) for (a) chitosan 30 g/L and (b) 50/50 mixture of CDchitosan and AD-chitosan at a total polymer concentration
4.43 g/L in 0.3 M AcOH/0.03 M AcONa. Reprinted with permission from J Phys Chem B. 2003; 107:8248–8254. Copyright 2006, American Chemical Society.
Table 10
Principal properties of chitosan in relation to its use in biomedical applications
Potential Biomedical applications
Principal characteristics
Surgical sutures
Dental implants
Artificial skin
Rebuilding of bone
Corneal contact lenses
Time release drugs for animals and humans
Encapsulating material
Biocompatible
Biodegradable
Renewable
Film forming
Hydrating agent
Nontoxic, biological tolerance
Hydrolyzed by lyzosyme
Wound healing properties
Efficient against bacteria, viruses, fungi
Table 11
Principal applications for chitosan
Agriculture
Water & waste treatment
Food & beverages
Cosmetics & toiletries
Biopharmaceutics
Defensive mechanism in plants
Stimulation of plant growth
Seed coating, Frost protection
Time release of fertilizers and nutrients into the soil
Flocculant to clarify water (drinking water, pools)
Removal of metal ions
Ecological polymer (eliminate synthetic polymers)
Reduce odors
Not digestible by human (dietary fiber)
Bind lipids (reduce cholesterol)
Preservative
Thickener and stabilizer for sauces
Protective, fungistatic, antibacterial coating for fruit
Maintain skin moisture
Treat acne
Improve suppleness of hair
Reduce static electricity in hair
Tone skin
Oral care (toothpaste, chewing gum)
Immunologic, antitumoral
Hemostatic and anticoagulant
Healing, bacteriostatic
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M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 n -Lauryl-carboxymethylchitosan is an amphiphilic polymer. It forms micelles that solubilize taxol, making it more effective therapeutically, and it is found to be safe in terms of membrane toxicity. This type of derivative is generally useful as a carrier for hydrophobic cancer drugs
Some recent advances in drug release should be mentioned. Films of chitosan incorporating prednisolone, formed by mixing have been tested for this purpose
. Chitosan gels and layer-by-layer polyelectrolyte capsules are often used for controlled release of drugs or proteins, as previously noted.
Chitosan and its derivatives have been used for gene transfection: for N -alkylated chitosan, it has been shown that transfection efficiency increases upon elongating the alkyl side chains and levels off when the number of carbons in the side chain exceeds 8
. Quaternized chitosan can be used for the same purpose
The physical properties of chitosan recommend it, for use in many types of devices
proteins and DNA can be assembled with a stimuliresponsive chitosan backbone.
Another point to note is biological activity in regard to agriculture since chitosan exhibits antivirus and antiphage activities
. It inhibits the growth of bacteria and bacterial infection, and stimulates the natural defenses in plants. A mechanism has been proposed via the ‘‘octadecanoid pathway’’
.
Alginate/chitosan systems have found applications as wound dressings and in bone tissue engineering
.
An interesting application concerns a self-setting calcium phosphate cement: chitosan glycerophosphate mixed with calcium phosphate and citric acid forms an injectable self-hardening system for bone repair or filling
4. Conclusion
623
Mucoadhesivity of chitosan and cationic derivatives is recognized and has been proved to enhance the adsorption of drugs especially at neutral pH;
N -trimethyl chitosan chloride interacts with negatively charged cell membranes
In this review we aim to present an overview of the state of art in the knowledge and technical applications of chitin and chitosan. We include an extensive bibliography of recent studies, both basic and applied. Nevertheless, this is an ambitious project; and the very large number of papers published on a wide range of properties and applications forces us to make a selection from the most significant results obtained by the many groups working around the world.
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Table 12
Specific characteristics for applications of chitosan in hair care
Properties
Aqueous solution interacting with negatively charged hair
(electrostatic interaction)
Antistatic effect (due to hydrophilic character), maintains moisture in low humidity and hair style in high humidity
Uses
Shampoos
Hair tonics
Rinses
Permanent wave agents
Hair colorants
Lacquers,
Hair sprays
Time release delivery (chitosan beads, gels or granules)
Removing sebum and oils from hairs (due to hydrophobic character)
Antibacterial and antifungal activity
Thickening polymer
Role in surfactant stability; stabilize emulsion
Make hair softer, increase mechanical strength
Protect elastic film on hairs, increasing their softness.
Chitin is a natural polymer for which we try to point out some unique features and its potential for useful development. It is important to bear in mind that its insolubility in ordinary solvents, makes chitin difficult to characterize and to process.
Though much work has been done to elucidate the morphology of chitin in the solid state, uncertainties still remain in the published record, and better parameters are still needed on a -chitin and hydrated b -chitin.
Chitin can be transformed and used as fiber, film, sponge or powder. The preparation of derivatives that are soluble, especially in aqueous media, makes it possible to take advantage of the special properties of chitin: this polysaccharide is a film-forming polymer, biodegradable and renewable; it also has antibacterial and fungistatic properties; the semi-rigid character of chitin is valuable for thickening properties but also promotes the inter-chain interactions that cause difficulties in characterization. Due to the diversity of sources of chitin and their state of organization in the solid state, the quality of commercial chitin available is not uniform and causes many difficulties during transformation and chemical modification. This is one of the factors that hinder the development of new uses. In addition, the high cost of extraction and purification of chitin seems to reserve this polymer to high added-value applications. For these reasons, it is assumed that biomedical and pharmaceutical applications are the most promising domains for development, with cosmetics in second place.
Similar conclusions can be drawn for chitosan, which is the most important derivative of chitin, even though the difficulty of controlling the distribution of the acetyl groups along the backbone makes it difficult to get reproducible initial polymers. Unlike chitin, chitosan is water soluble in acidic media, or under precisely specified conditions at neutral pH, allowing much development in the domains of solutions and hydrogels.
The advantage of chitosan over other polysaccharides (cellulose, starch, galactomannans, etc.) is that its chemical structure allows specific modifications without too many difficulties at the C-2 position, as described in this review. Specific groups can be introduced to design polymers for selected applications.
Finally, the natural biological properties of chitin and chitosan are valuable for both plant and animal applications, and such developments can be considered as valuable extensions of the use of chitin and its derivatives.
Acknowledgments
The author thanks Henri Chanzy (CERMAV-
Grenoble) for valuable information regarding the solid-state structure of chitin and Karim Mazeau
(CERMAV-Grenoble) for the molecular modelling of chitin and chitosan.
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References
[1] Rudall KM, Kenchington W. The chitin system. Biol Rev
1973;40:597–636.
[2] Blackwell J. Chitin. In: Walton AG, Blackwell J, editors.
Biopolymers. New York: Academic Press; 1973. p. 474–89.
[3] Rudall KM. Chitin and its association with other molecules. J Polym Sci Part C 1969;28:83–102.
[4] Atkins EDT. Conformation in polysaccharides and complex carbohydrates. J Biosci 1985;8:375–87.
[5] Olivera BM, Hillyard DR, Marsh M, Yoshikami D.
Combinatorial peptide libraries in drug design: lesson from venomous cone snails. TIBTECH 1995;13:422–6.
[6] Atkins EDT, Dlugosz J, Foord S. Electron diffraction and electron microscopy of crystalline a -chitin from the grasping spines of the marine worm Sagitta . Int J Biol
Macromol 1979;1:29–32.
[7] Saito Y, Okano T, Chanzy H, Sugiyama J. Structural study of a -chitin from the grasping spine of the arrow worm
( Sagitta spp.). J Struct Biol 1995;114:218–28.
[8] Chanzy H. Chitin crystals. In: Domard A, Roberts GAF,
Va˚rum KM, editors. Advances in chitin science. Lyon,
France: Jacques Andre´; 1998. p. 11–21.
[9] Chre´tiennot-Dinet M-J, Giraud-Guille M-M, Vaulot D,
Putaux J-L, Chanzy H. The chitinous nature of filament ejected by Phaeocystis (Prymnesiophycae). J Phycol
1997;33:666–72.
[10] Rudall KM. Molecular structure in arthropod cuticles. In:
Hepburn HR, editor. The insect integument. Amsterdam:
Elsevier Scientific; 1976. p. 21–41.
[11] Persson JE, Domard A, Chanzy H. Single crystals of a -chitin. Int J Biol Macromol 1990;13:221–4.
[12] Helbert W, Sugiyama J. High-resolution electron microscopy on cellulose II and a -chitin single crystals. Cellulose
1998;5:113–22.
[13] Ruiz-Herrera J, Sing VO, Van der Woude WJ, Bartnicki-
Garcia S. Microfibril assembly by granules of chitin synthetase. Proc Nat Acad Sci USA 1975;72:2706–10.
[14] Bartnicki-Garcia S, Persson J, Chanzy H. An electron microscope and electron diffraction study of the effect of calcofluor and congo red on the biosynthesis of chitin in vitro. Arch Biochem Biophys 1994;310:6–15.
[15] Sakamoto J, Sugiyama J, Kimura S, Imai T, Itoh T,
Watanabe T, et al. Artificial chitin spherulites composed of single crystalline ribbons of a -chitin via enzymatic polymerization. Macromolecules 2000;33:4155–60.
[16] Blackwell J, Parker KD, Rudall KM. Chitin in pogonophore tubes. J Mar Biol Assoc UK 1965;45:659–61.
[17] Gaill F, Persson J, Sugiyama P, Vuong R, Chanzy H. The chitin system in the tubes of deep sea hydrothermal vent worms. J Struct Biol 1992;109:116–28.
[18] Lotmar W, Picken LER. A new crystallographic modification of chitin and its distribution. Experientia 1950;6:
58–9.
[19] Herth W, Kuppel A, Schnepf E. chitinous fibrils in the lorica of the flagellate chrysophyte Poterioochromonas stipitata (syn.
Ochromonas malhamensis ). J Cell Biol
1977;73:311–21.
[20] Herth W, Mulisch M, Zugenmaier P. Comparison of chitin fibril structure and assembly in three unicellular organisms.
In: Muzzarelli R, Jeuniaux C, Gooday GW, editors. Chitin
625 in nature and technology. New York: Plenum Publishing
Corporation; 1986. p. 107–20.
[21] Dweltz NE, Colvin JR, McInnes AG. Studies on chitin
( b -(1
-
4)-linked 2-acetamido-2-deoxy-
D
-glucan) fibers from the diatom Thalassiosira fluviatilis , Hustedt. III. The structure of chitin from X-ray diffraction and electron microscope observations. Can J Chem 1968;46:1513–21.
[22] Revol J-F, Chanzy H. High-resolution electron microscopy of b -chitin microfibrils. Biopolymers 1986;25:1599–601.
[23] Gonell HW. Ro¨tgenographische studien an chitin. Z
Physiol Chem 1926;152:18–30.
[24] Clark GL, Smith AF. X-ray studies of chitin, chitosan, and derivatives. J Phys Chem 1936;40:863–79.
[25] Gardner KH, Blackwell J. Refinement of the structure of b -chitin. Biopolymers 1975;14:1581–95.
[26] Minke R, Blackwell J. The structure of a -chitin. J Mol Biol
1978;120:167–81.
[27] Blackwell J. Structure of b -chitin or parallel chain systems of polyb -(1 4)-N-acetyl-
D
-glucosamine.
Biopolymers
1969;7:281–98.
[28] Rossle M, Flot D, Engel J, Burghammer M, Riekel C,
Chanzy H. Fast intracrystalline hydration of b -chitin revealed by combined microdrop generation and on-line synchrotron radiation microdiffraction. Biomacromolecules 2003;4:981–6.
[29] Saito Y, Okano T, Putaux J-L, Gaill F, Chanzy H.
Crystallosolvates of b -chitin and alcohols. In: Domard A,
Roberts GAF, Va˚rum KM, editors. Advances in chitin science. Lyon, France: Jacques Andre´; 1998. p. 507–12.
[30] Noishiki Y, Nishiyama Y, Wada M, Okada S, Kuga S.
Inclusion complexes of b -chitin an aliphatic amines.
Biomacromolecules 2003;4:944–9.
[31] Noishiki N, Kuga S, Wada M, Hori K, Nishiyama Y.
Guest selectivity in complexation of b -chitin. Macromolecules 2004;37:6839–42.
[32] Noishiki Y, Nishiyama Y, Wada M, Kuga S. Complexation of a -chitin with aliphatic amines. Biomacromolecules
2005;6:2362–4.
[33] Rudall KM. The chitin/protein complexes of insect cuticles.
Adv Insect Physiol 1963;1:257–313.
[34] Saito Y, Okano T, Gaill F, Chanzy H, Putaux J-L.
Structural data on the intra-crystalline swelling of b -chitin.
Int J Biol Macromol 2000;28:81–8.
[35] Saito Y, Putaux J-L, Okano T, Gaill F, Chanzy H.
Structural aspects of the swelling of b -chitin in HCl and its conversion into a -chitin. Macromolecules 1997;30:
3867–73.
[36] Darmon SE, Rudall KM. Infra-red and X-ray studies of chitin. Disc Faraday Soc 1950;9:251–60.
[37] Pearson FG, Marchessault RH, Liang CY. Infrared spectra of crystalline polysaccharides. V. Chitin. J Polym Sci
1960;13:101–16.
[38] Falk M, Smith DG, McLachlan J, McInnes AG. Studies on chitin ( b -(1
-
4)-linked 2-acetamido-2-deoxy-
D
-glucan) fibers of the diatom Thalassiosira fluviatilis Hustedt. II.
Proton magnetic resonance, infrared, and X-ray studies.
Can J Chem 1966;44:2269–81.
[39] Galat A, Koput J, Popowicz J. Analyses of infrared amide bands of chitin. Acta Biochim Polonica 1979;26:303–8.
[40] Iwamoto R, Miya M, Mima S. Vibrational polarization spectra of a -type chitin. In: Hirano S, Tokura S, editors.
Chitin and chitosan. Proceedings of the second interna-
626
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 tional conference on chitin and chitosan. Sapporo: The
Japanese Society of Chitin and Chitosan; 1982. p. 82–6.
[41] Focher B, Naggi A, Torri G, Cosani A, Terbojevich M.
Structural differences between chitin polymorphs and their precipitates from solutions-evidence from CP-MAS
13
C-
NMR, FT-IR and FT-Raman spectroscopy. Carbohydr
Polym 1992;17:97–102.
[42] Brugnerotto J, Lizardi J, Goycoolea FM, Argu¨elles-Monal
W, Desbrie`res J, Rinaudo M. An infrared investigation in relation with chitin and chitosan characterization. Polymer
2001;42:3559–80.
[43] Saito H, Tabeta R, Hirano S. Conformation of chitin and
Nacyl chitosans in solid state as revealed by
13
C cross polarization/magic angle spinning (CP/MAS) NMR spectroscopy. Chem Lett 1981:1479–82.
[44] Tanner SF, Chanzy H, Vincendon M, Roux J-C, Gaill F.
High resolution solid-state carbon-13 nuclear magnetic resonance study of chitin. Macromolecules 1990;23:
3576–83.
[45] Kono H. Two-dimensional magic angle spinning NMR investigation of naturally occurring chitins: precise
1
H and
13
C resonance assignment of a - and b -chitin. Biopolymers
2004;75:255–63.
[46] Mathur NK, Narang CK. Chitin and chitosan, versatile polysaccharides from marine animals. J Chem Educ 1990;
67:938–42.
[47] Kurita K, Tomita K, Ishi S, Nishimura S-I, Shimoda K.
b -chitin as a convenient starting material for acetolysis for efficient preparation of N -acetylchitooligosaccharides.
J Polym Sci A Polym Chem 1993;31:2393–5.
[48] (a) Austin PR. Chitin solvents and solubility parameters.
In: Zikakis JP, editor. Chitin and chitosan and related enzymes.
Orlando: Academic Press, Inc.; 1984.
p. 227–37
(b) Austin PR. Solvents for and purification of chitin.
USpatent 3,892,731; 1975 and Purification of chitin.
USPatent 3,879, 377; 1975.
[49] McCormick CL, Callais PA, Hutchinson BH. Solution studies of cellulose in lithium chloride N,N -dimethylacetamide. Macromolecules 1985;18:2394–401.
[50] (a) Tamura H, Hamaguchi T, Tokura S. Destruction of rigid crystalline structure to prepare chitin solution. In:
Advances in chitin science, vol. 7. ISM BioPolymer
Inc.; 2003. p. 84–7
(b) Carpozza RC. Spinning and shaping poly-( Nacetyl-
D
glucosamine). US Patent 3,988, 411; 1976 and Solution of poly-( N -acetyl-
D
-glucosamine). US Patent 3,989,535;
1976.
[51] (a) Einbu A, Naess SN, Elgsaeter A, Va˚rum KM. Solution properties of chitin in alkali. Biomacromolecules
2004;5:2048–54;
(b) Poirier M, Charlet G. Chitin fractionation and characterization in N, N -dimethylacetamide/lithium chloride solvent system. Carbohydr Polym 2002;50:
363–70.
[52] Terbojevich M, Carraro C, Cosani A. Solution studies of the chitin-lithium chloride-N, N-dimethylacetamide system. Carbohydr Res 1988;180:73–86.
[53] Vincendon M. Solution of chitin in phosphoric acid. In:
Karniki SZ, editor. Chitin world. Bremerhaven, Germany:
Wirtschaftsverlag NW; 1994. p. 91–7.
[54] (a) Gagnaire D, Saint-Martin J, Vincendon M. NMR studies of chitin and chitin derivatives. Makromol
Chem 1982;183:593–601;
(b) Vincendon M.
1
H NMR study of the chitin dissolution mechanism. Makromol Chem 1985;186:1787–95.
[55] Sannan T, Kurita K, Iwakura Y. Studies on chitin, 1.
Makromol Chem 1975;176:1191–5.
[56] Sannan Y, Kurita K, Iwakura Y. Studies on chitin, vol. 2.
Makromol Chem 1976;177:3589–600.
[57] Kubota N, Eguchi Y. Facile preparation of water-soluble
N-acetylated chitosan and molecular weight dependence of its water-solubility. Polym J 1997;29:123–7.
[58] Argu¨elles-Monal W, Goycoolea FM, Lizardi J, Peniche C,
Higuera-Ciapara I. Chitin and chitosan in gel network systems. In: Bohidar HB, Dubin P, Osada Y, editors.
Polymer gels. ACS Symposium Series No. 833. Washington
D.C.: American Chemical Society; 2003. p. 102–22.
[59] Goycoolea FM, Arguelles-Monal WM, Lizardi J, Peniche
C, Heras A, Galed G, Diaz EI. Temperature and pHsensitive chitosan hydrogels: DSC, rheological and swelling evidence of a volume phase transition. Polym Bull, 2006, in press.
[60] Aiba S. Studies on chitosan: 3. Evidence for the presence of random and block copolymer struc tures in partially N acetylated chitosans. Int J Biol Macromol 1991;13:40–4.
[61] Cho Y-W, Jang J, Park CR, Ko S-W. Preparation and solubility in acid and water of partially deacetylated chitins.
Biomacromolecules 2000;1:609–14.
[62] Maghami GG, Roberts GAF. Evaluation of the viscometric constants for chitosan. Makromol Chem 1988;189:
195–200.
[63] Toffey A, Samaranayake G, Frazier CE, Glasser WG.
Chitin derivatives. I. Kinetics of the heat-induced conversion of chitosan to chitin. J Appl Polym Sci 1996;60:75–85.
[64] Toffey A, Glasser WG. Chitin derivatives. II. Time–temperature-transformation cure diagrams of the chitosan amidization process. J Appl Polym Sci 1999;73:
1879–89.
[65] (a) Muzzarelli RAA. Chitin. In: Mark HF, Bikales NM,
Overberger CG, Menges G, editors. EPST. vol. 3. 2nd ed. New York: Wiley; 1985. p. 430–49.
(b) Hudson SM, Jenkins DW. Chitin and chitosan. In:
Mark HF, editor. EPST. vol. 1. 3rd ed. New York:
Wiley; 2003. p. 569–80.;
(c) Muzzarelli RAA. Chitin. In: Aspinall GO, editor. The polysaccharides, vol. 3. London: Academic Press; 1985.
p. 417–47.
[66] Wang A, Li P, Li Q, Gao F. Studies on modification and application of chitin. Zhongguo Haiyang Yaowu 1997;16:
14–7.
[67] Park IK, Park YH. Preparation and structural characterization of water soluble O -hydroxypropyl chitin derivatives. J Appl Polym Sci 2001;80:2624–32.
[68] Chow KS, Khor E. New fluorinated chitin derivatives: synthesis, characterization and cytotoxicity assessment.
Carbohydr Polym 2001;47:357–63.
[69] Tokura S, Itoyama K, Nishi N, Nishimura S, Saiki I,
Azuma I. Selective sulfation of chitin derivatives for biomedical functions. J Macromol Sci, Pure Appl Chem
1994;A31:1701–18.
[70] Tokura S, Saiki I, Murata J, Makabe T, Tsuta Y, Azuma I.
Inhibtion of tumor-induced angiogenesis by sulphated
chitin derivatives. In: Brine CJ, Sandford PA, Zikakis JP, editors. Advances in chitin and chitosan. London and
New York: Elsevier; 1992. p. 87–95.
[71] Kurita K, Koyama Y, Inoue S, Nishimura S. ((Diethylamino) ethyl) chitins: preparation and properties of novel aminated chitin derivatives. Macromolecules 1990;23:
2865–9.
[72] Andrew CA, Khor E, Hastings GW. The influence of anionic chitin derivatives on calcium phosphate crystallization. Biomaterials 1998;19:1309–16.
[73] Yoshino H, Ishii S, Nishimura S, Kurita K. Preparation and characterization of mercapto-chitin derivatives. In:
Brine CJ, Sandford PA, Zikakis JP, editors. Advances in chitin and chitosan. London and New York: Elsevier; 1992.
p. 565–70.
[74] Vincendon M. Chitin carbamates. In: Brine CJ, Sandford
PA, Zikakis JP, editors. Advances in chitin and chitosan.
London and New York: Elsevier; 1992. p. 556–64.
[75] Rinaudo M, Reguant J. Polysaccharide derivatives. In:
Frollini E, Lea˜o AL, Mattoso LHC, editors. Natural polymers and agrofibers composites. Sa˜o Carlos, Bre´sil:
CIP-BRASIL; 2000. p. 15–39.
[76] Ren L, Miura Y, Nishi N, Tokura S. Modification of chitin by ceric salt-initiated graft polymerization-preparation of poly(methylmethacrylate)-grafted chitin derivatives that swell in organic solvents. Carbohydr Polym 1993;21:23–7.
[77] Kurita K, Inoue S. Preparation of iodo-chitins and graft copolymerization onto the derivatives. In: Skjak-Braek G,
Anthonsen T, Sandford P, editors. Chitin and chitosan.
Sources, chemistry, biochemistry, physical properties and applications. London and New York: Elsevier; 1989.
p. 365–72.
[78] Rupley JA. The hydrolysis of chitin by concentrated hydrochloric acid, and the preparation of low-molecular weight substrates for lysozyme. Biochim Biophys Acta
1964;83:245–55.
[79] Sashiva H, Saimoto H, Sgigemasa Y, Ogawa R, Tokura S.
Lysozyme susceptibility of partially deacetylated chitin. Int
J Biol Macromol 1990;12:295–6.
[80] Datta PK, Basu PS, Datta TK. Isolation and characterization of Vicia faba lectin affinity purified on chitin column.
Prep Biochem 1984;14:373–87.
[81] Krajewska B. Application of chitin- and chitosan-based materials for enzyme immobilizations: a review. Enzyme
Microbiol Technol 2004;35:126–39.
[82] (a) Songkroah C, Nakbanpote W, Thiravetyan P. Recovery of silver–thiosulfate complexes with chitin. Process
Biochem 2004;39:1553–9;
(b) Kosyakov VN, Yakovlev NG, Veleshko IE. Application of chitin-containing fiber material ‘‘mycoton’’ for actinide adsorption. J Nucl Sci Technol 2002(suppl. 3):
508–11.
[83] Austin PR, Brine J. Chitin films and fibers. USPatent
4,029,727; 1977.
[84] Hirano S. Wet-spinning and applications of functional fibers based on chitin and chitosan. In: Arguelles-Monal W, editor. Natural and synthetic polymers: challenges and perspectives. Macromol Symp, vol. 168. Weinheim, Germany: Wiley-VCH Verlag GmbH; 2001. p. 21–30.
[85] Hirano S, Midorikawa T. Novel method for the preparation of Nacylchitosan fiber and N -acylchitosan–cellulose fiber. Biomaterials 1998;19:293–7.
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 627
[86] Hirano S, Nakahira T, Nakagawa M, Kim SK. The preparation and applications of functional fibres from crab shell chitin. J Biotechnol 1999;70:373–7.
[87] (a) Tokura S, Nishi N. Preparation and properties of alkylchitin fibers. In: Hirano S, Tokura S, editors. Chitin chitosan. In: Proceeding of the international conference, 2d. Jpn. Soc. Chitin Chitosan, Tattori, Japan.
1982. p. 244–7.
(b) Kobayashi Y, Nishiyama M, Matsuo R, Tokura S,
Nishi N. Application of chitin and its derivatives to paper industry. In: Hirano S, Tokura S, editors. Chitin chitosan. In: Proceeding of the International Conference, 2d. Jpn Soc Chitin Chitosan, Tattori, Japan.
1982. p. 244–7.
[88] Yusof NL, Wee A, Lim LY, Khor E. Flexible chitin films as potential wound-dressing materials: wound model studies. J Biomed Mater Res A 2003;66A:224–32.
[89] (a) Hudson SM. Applications of chitin and chitosan as fiber and textile chemicals. In: Domard A, Roberts
GAF, Va˚rum KM, editors. Advances in chitin science, vol. 2. Lyon (France): Jacques Andre´ Publ.; 1998.
p. 590–9;
(b) Hudson SM. The applications of chitin and chitosan to fiber and textile products. In: Chen RH, Chen HC, editors. Advances in chitin science, vol. 3. Taiwan:
National Taiwan Ocean University; 1999. p. 80–7;
(c) Rathke TD, Hudson SM. Review of chitin and chitosan as fiber and film formers. Rev Macromol
Chem Phys 1994;C34:375–437.
[90] Kanke M, Katayama H, Tsuzuki S, Kuramoto H.
Application of chitin and chitosan to pharmaceutical preparations. Chem Pharm Bull 1989;37:523–5.
[91] Kato Y, Onishi H, Machida Y. Application of chitin and chitosan derivatives in the pharmaceutical field. Curr
Pharm Biotechnol 2003;4:303–9.
[92] Ito M, Matahira Y, Sakai K. The application of chitinchitosan to bone filling materials, vol. 4. Kichin, Kitosan
Kenkyu: Publ. Nippon Kichin, Kitosan Gakkai; 1998
(p. 142–143).
[93] (a) Hirano S, Horiuchi K. Chitin gels. Int J Biol Macromol
1989;11:253–4;
(b) Zhang M, Kohr E, Hirano S. Hydrogels of chitin and chitosan. In: Nishinari K, Doi E, editors. Food hydrocolloids: structures, properties and functions.
New York: Plenum Press; 1994. p. 65–70.
[94] Ouchi T, Inosaka K, Murata J, Nishimoto T, Ohya Y.
Design of water-soluble CM-chitin/antitumor drug conjugate. Polym Prep, Am Chem Soc, Div Polym Chem
1992;33(2):537–8.
[95] Khan W, Prithiviraj B, Smith DL. Effect of foliar application of chitin and chitosan oligosaccharides on photosynthesis of maize and soybean. Photosynthetica
2002;40:621–4.
[96] Cartier N, Domard A, Chanzy H. Single crystals of chitosan. Int J Biol Macromol 1990;12:289–94.
[97] Ogawa K. Effect of heating an aqueous suspension of chitosan on the crystallinity and polymorphs. Agric Biol
Chem 1991;55:2375–9.
[98] Ogawa K, Yui T, Miya M. Dependence on the preparation procedure of the polymorphism and crystallinity of chitosan membranes. Biosci Biotech Biochem 1992;56:
858–62.
628
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
[99] Domard A, Rinaudo M. Preparation and characterization of fully deacetylated chitosan. Int J Biol Macromol 1983;5:
49–52.
[100] Rinaudo M, Domard A. Solution properties of chitosan.
In: Skjak-Braek G, Anthonsen T, Sandford P, editors.
Chitin and chitosan. Sources, chemistry, biochemistry, physical properties and applications.
London and
New York: Elsevier; 1989. p. 71–86.
[101] Rinaudo M, Pavlov G, Desbrie`res J. Influence of acetic acid concentration on the solubilization of chitosan.
Polymer 1999;40:7029–32.
[102] Rinaudo M, Pavlov G, Desbrie`res J. Solubilization of chitosan in strong acid medium. Int J Polym Anal Charact
1999;5:267–76.
[103] Domard A. pH and CD measurements on fully deacetylated chitosan: application to Cu II—Polymer interactions.
Int J Biol Macromol 1987;9:98–104.
[104] Chenite A, Chaput C, Wang D, Combes C, Buschmann
MD, Hoemann CD, et al. Novel injectable neutral solutions of chitosan form biodegradable gels in situ.
Biomaterials 2000;21:2155–61.
[105] Chenite A, Buschmann M, Wang D, Chaput C, Kandani
N. Rheological characterization of thermogelling chitosan/ glycerol-phosphate solutions. Carbohydr Polym 2001;46:
39–47.
[106] Molinaro G, Leroux JC, Damas J, Adam A. Biocompatibility of thermosensitive chitosan-based hydrogels: an in vivo experimental approach to injectable biomaterials.
Biomaterials 2002;23:2717–22.
[107] Cho J, Heuzey MC, Beguin A, Carreau PJ. Physical gelation of chitosan in the presence of b -glycerophosphate: the effect of temperature. Biomacromolecules 2005;6:
3267–75.
[108] Rusu-Balaita L, Desbrie`res J, Rinaudo M. Formation of a biocompatible polyelectrolyte complex: chitosan-hyaluronan complex stability. Polym Bull 2003;50:91–8.
[109] Miya M, Iwamoto R, Yoshikawa S, Mima S. I.R.
spectroscopic determination of CONH content in highly deacylated chitosan. Int J Biol Macromol 1980;2:323–4.
[110] Baxter A, Dillon M, Taylor KD, Roberts GAF. Improved method for I.R. determination of the degree of N acetylation of chitosan. Int J Biol Macromol 1992;14:
166–9.
[111] Domszy JG, Roberts GAF. Evaluation of infrared spectroscopic techniques for analysing chitosan. Makromol Chem
1985;186:1671–7.
[112] Pelletier A, Lemire I, Sygusch J, Chornet E, Overend RP.
Chitin/chitosan transformation by thermo-mechano-chemical treatment including characterization by enzymic depolymerization. Biotechnol Bioeng 1990;36:310–5.
[113] Muzzarelli RAA, Rochetti R. Determination of the degree of acetylation of chitosans by first derivative ultraviolet spectrophotometry. Carbohydr Polym 1985;5:461–72.
[114] Rinaudo M, Le Dung P, Gey C, Milas M. Substituent distribution on O , N -carboxymethylchitosans by
13
C NMR. Int J Biol Macromol 1992;14:122–8.
1
H and
[115] Saito H, Tabeta R, Ogawa K. High-resolution solid-state
13
C NMR study of chitosan and its salts with acids: conformational characterization of polymorphs and helical structures as viewed from the conformation-dependent
13
C chemical shifts. Macromolecules 1987;20:2424–30.
[116] Raymond L, Morin FG, Marchessault RH. Degree of deacetylation of chitosan using conductometric titration and solid-state NMR. Carbohydr Res 1993;246:
331–6.
[117] Heux L, Brugnerotto J, Desbrie`res J, Versali M F, Rinaudo
M. Solid state NMR for determination of degree of acetylation of chitin and chitosan. Biomacromolecules
2000;1:746–51.
[118] Va˚rum KM, Anthonsen MW, Grasdalen H, Smisrød O.
Determination of the degree of N -acetylation and the distribution of N -acetyl groups in partially N -deacetylated chitins (chitosans) by high-field n.m.r. spectroscopy.
Carbohydr Res 1991;211:17–23.
[119] Va¨rum KM, Anthonsen MW, Grasdalen H, Smisrød O.
13
C-NMR studies of the acetylation sequences in partially
N -deacetylated chitins (chitosans).
Carbohydr Res
1991;217:19–27.
[120] Philippova OE, Volkov EV, Sitnikova NL, Khokhlov A,
Desbrie`res J, Rinaudo M. Two types of hydrophobic aggregates in aqueous solutions of chitosan and its hydrophobic derivative. Biomacromolecules 2001;2:
483–90.
[121] Roberts GA, Domszy JG. Determination of the viscometric constants for chitosan. Int J Biol Macromol 1982;4:374–7.
[122] Lee VFP. Solution and shear properties of chitin and chitosan. PhD dissortation. University of Washington
(USA), 1974.
[123] Rinaudo M, Milas M, Le Dung P. Characterization of chitosan. Influence of ionic strength and degree of acetylation on chain expansion. Int J Biol Macromol
1993;15:281–5.
[124] Brugnerotto J, Desbrie`res J, Roberts G, Rinaudo M.
Characterization of chitosan by steric exclusion chromatography. Polymer 2001;42:9921–7.
[125] Berth G, Dautzenberg H. The degree of acetylation of chitosans and its effect on the chain conformation in aqueous solution. Carbohydr Polym 2002;47:39–51.
[126] Roberts GAF, Wood FA. A study of the influence of structure on the effectiveness of chitosan as an anti-felting treatment for wool. J Biotechnol 2001;89:297–304.
[127] (a) Mazeau K, Perez S, Rinaudo M. Predicted influence of
N -acetyl group content on the conformational extension of chitin and chitosan chains. J Carbohydr Chem
2000;19:1269–84;
(b) Mazeau K, Rinaudo M. The prediction of the characteristics of some polysaccharides from molecular modelling. Comparison with effective behaviour. Food
Hydrocolloids 2004;18(6):885–98.
[128] Allan GG, Peyron M. Molecular weight manipulation of chitosan I: kinetics of depolymerization by nitrous acid.
Carbohydr Res 1995;277:257–72.
[129] Allan GG, Peyron M. Molecular weight manipulation of chitosan II: prediction and control of extend of depolymerization by nitrous acid. Carbohydr Res 1995;277:273–82.
[130] Anthonsen MW, Va˚rum KM, Smidsrød O. Solution properties of chitosans: conformation and chain stiffness of chitosans with different degrees of N -acetylation.
Carbohydr Polym 1993;22:193–201.
[131] Va˚rum KM, Smidsrød O. Structure–properties relationship in chitosans. In: Dumitriu S, editor. Polysaccharides.
Structural diversity and functional versatility. 2nd ed.
New York: Marcel Dekker; 2005. p. 625–42.
[132] Bulher E, Rinaudo M. Structural and dynamical properties of semirigid polyelectrolyte solutions: a light-scattering study. Macromolecules 2000;33:2098–106.
[133] Bulher E, Guetta O, Rinaudo M. Characterization of semiflexible polyelectrolyte solutions in the presence of excess salt: from dilute to semidilute regime. Int J Polym
Anal Charact 2000;6:155–75.
[134] Odijk T. On the ionic-strength dependence of the intrinsic viscosity of DNA. Biopolymers 1979;18:3111–3.
[135] Reed W. Light-scattering results on polyelectrolyte conformations, diffusion and interparticles interactions and correlations. In: Schmitz KS, editor. Macroion characterization. From dilute solution to complex fluids. ACS
Symposium series 548. New York: American Chemical
Society; 1984. p. 297–314.
[136] Brugnerotto J, Desbrie`res J, Heux L, Mazeau K, Rinaudo
M. Overview on structural characterization of chitosan molecules in relation with their behavior in solution.
Macromol Symp 2001;168:1–20.
[137] Yamakawa H, Fujii M. Intrinsic viscosity of wormlike chains. Determination of the shift factor. Macromolecules
1974;7:128–35.
[138] Terbojevich M, Cosani A. Chitosan: chain rigidity and mesophase formation. Carbohydr Res 1991;209:251–60.
[139] (a) Wang W, Bo S, Li S, Qin W. Determination of the
Mark–Houwink equation for chitosans with different degrees of deacetylation. Int J Biol Macromol 1991;13:
281–5;
(b) Wang W, Qin W, Bo S. Influence of the degree of deacetylation of chitosan on its Mark–Houwink equation parameters. Makromol Chem Rapid Commun 1991;12:559–61.
[140] Muzzarelli RAA, editor. Natural chelating polymers: alginic acid, chitin and chitosan. New York: Pergamon
Press; 1973.
[141] Ogawa K, Miganiski T, Hirano S. X-ray diffraction study on chitosan–metal complexes. In: Zikakis JP, editor.
Advances in chitin, chitosan and related enzymes. Orlando:
Academic Press, Inc.; 1984. p. 327–45.
[142] Rhazi M, Desbrie`res J, Tolaimate A, Rinaudo M, Vottero
P, Alagui A. Contribution to the study of the complexation of copper by chitosan and oligomers. Polymer 2002;43:
1267–76.
[143] Kurita K, Sannan T, Iwakura Y. Studies on chitin. VI.
Binding of metal cations. J Appl Polym Sci 1979;23:511–5.
[144] Rhazi M, Desbrie`res J, Tolaimate A, Rinaudo M, Vottero
P, Alagui A, et al. Influence of the nature of the metal ions on the complexation with chitosan. Application to the treatment of liquide waste. Eur Polym J 2002;38:1523–30.
[145] Mitani T, Fukumuro N, Yoshimoto C, Ishii H. Effect of counter ions(SO
2
4 and Cl ) on the adsorption of copper and nickel ions by swollen chitosan beads. Agric Biol Chem
1991;55:2419.
[146] (a) Peniche-Covas C, Alvarez LW, Arguelles-Monal W.
The adsorption of mercuric ions by chitosan. J Appl
Polym Sci 1992;46:1147–50;
(b) Peniche-Covas C, Jimenez MS. Characterization of silver-binding chitosan by thermal analysis and electron impact mass spectrometry. Carbohydr Polym
1988;9:249–56.
[147] Ruiz M, Sastre A, Guibal E. Influence of drying process of chitosan beads on Pt and Pd sorption. In: Muzzarelli RAA,
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 629
Muzzarelli C, editors. Chitosan in pharmacy and chemistry. Grottammare (Italy): ATEC; 2002. p. 341–51.
[148] Annachhatre AP, Win NN, Chandrkrachang S. Adsorption of copper on chitosan. In: Stevens WF, Rao MS,
Chandrkrachang S, editors. Chitin and chitosan—environmental friendly and versatile biomaterials. Proceedings of the second Asia Pacific Symposium. 1996. p. 169–73.
[149] Nieto JM, Peniche-Covas C, Del Bosque J. Preparation and characterization of a chitosan–Fe (III) complex.
Carbohydr Polym 1992;18:221–4.
[150] Bhatia SC, Ravi N. A magnetic study of an Fe–chitosan complex and its relevance to other biomolecules. Biomacromolecules 2000;1:413–7.
[151] Ogawa K, Oka K, Yui T. X-ray study of chitosan–transition metal complex. Chem Mater 1993;5:726–8.
[152] Gomez-Guillen M, Gomez-Sanchez A, Martin-Zamora M
E. A derivative of chitosan and 2, 4-pentanedione with strong chelating properties. Carbohydr Res 1992;233:
255–9.
[153] Chiessi E, Paradossi G, Venanzi M, Pispisa B. Association complexes between Fe(III) or Cu(II) ions and chitosan derivatives. A thermodynamic and spectroscopic investigation. Int J Biol Macromol 1993;15:145–51.
[154] Hall LD, Yalpani M. Derivatives of chitins, chitosans and other polysaccharides. US Patent 4,424,346; 1984.
[155] Muzzarelli RAA, Tanfani F, Mariotti S, Emanuelli M.
N -
( o -carboxybenzyl) chitosans: novel chelating polyampholytes. Carbohydr Polym 1982;2:145–57.
[156] Muzzarelli RAA, Tanfani F, Mariotti S, Emanuelli M.
N -
(carboxymethyllidene)chitosans and N -carboxymethyl)chitosans: novel chelating polyampholytes obtained from chitosan glyoxylate. Carbohydr Res 1982;107:199–214.
[157] Muzzarelli RAA. Amphoteric derivatives of chitosan and their biological significance. In: Skjak-Braek G, Anthonsen
T, Sandford P, editors. Chitin and chitosan. Sources, chemistry, biochemistry, physical properties and applications. London and New York: Elsevier; 1989. p. 87–99.
[158] Desbrie`res J, Rinaudo M, Babak V, Vikhoreva V. Surface activity of water soluble amphiphilic chitin derivatives.
Polym Bull 1997;39:209–15.
[159] Babak VG, Rinaudo M. Physico-chemical properties of chitin-surfactant complexes. In: Muzzarelli RAA, Muzzarelli C, editors. Chitosan in pharmacy and chemistry.
Grottammare (Italy): ATEC; 2002. p. 277–84.
[160] Desbrie`res J, Rinaudo M. Interactions between chitin derivatives and surfactants. In: El-Nokaly MA, Soini HA, editors. Polysaccharide applications: cosmetics and pharmaceuticals. ACS Symposium Series 1999; 737. p. 199–213.
[161] (a) Babak VG, Merkovich EA, Desbrie`res J, Rinaudo M.
Formation of an ordered nanostructure in surfactant–polyelectrolyte complexes formed by interfacial diffusion. Polym Bull 2000;45:77–81;
(b) Babak V, Lukina I, Vikhoreva G, Desbrie`res J,
Rinaudo M. Interfacial properties of dynamic association between chitin derivatives and surfactants. Colloids Surf A: Physicochem Eng Aspects 1999;147:
139–48;
(c) Babak VG, Merkovich EA, Galbraikh LS, Shtykova EV,
Rinaudo M. Kinetics of diffusionally induced elation and ordered nanostructure formation in surfactant–polyelectrolyte complexes formed at water/water emulsion type interfaces. Mendeleyev Commun 2000;3:94–5.
630
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
[162] Babak V, Kildeyeva N, Merkovich E. The production of chitosan–surfactant complex gel capsules for enzyme delivery. In: Poceedings of the 28th international symposium on controlled release of bioactive materials and 4th consumer & diversified products conference. vol. 2, San
Diego, CA; 2001. p. 940–41.
[163] Prado A, Macedo JL, Dias CL, Dias JA. Calorimetric studies of the association of chitin and chitosan with sodium dodecyl sulfate. Colloids Surf B Biointerfaces
2004;35:23–7.
[164] Thongngam M, McClements DJ. Influence of pH, ionic strength and temperature on self-association and interactions of sodium dodecyl sulphate in the absence and presence of chitosan. Langmuir 2005;21:79–86.
[165] Thongngam M, McClements D J. Characterization of interactions between chitosan and an anionic surfactant.
J Agric Food Chem 2004;52:987–91.
[166] Nonaka K-I, Kazama S, Goto A, Fukuda H, Yoshioka H,
Yoshioka H. Spin probe study on the interaction of chitosan-derived polymer surfactants with lipid membrane.
J Colloid Interface Sci 2002;246:288–95.
[167] Peniche C, Arguelles-Monal W. Chitosan based Polyelectrolyte complexes. Macromol Symp 2001;168:103–16.
[168] Arguelles-Monal W, Peniche C. Study of the interpolyelectrolyte reaction between chitosan and carboxymethylcellulose. Makromol Chem Rapid Commun 1988;9:693–7.
[169] Vasiliu S, Popa M, Rinaudo M. Polyelectrolyte capsules made of two biocompatible natural polymers. Eur Polym
J 2005;41:923–32.
[170] Kubota N, Kikuchi Y. Macromolecular complexes of chitosan. In: Dumitriu S, editor. Polysaccharides. Structural diversity and functional versatility. New York: Marcel
Dekker, Inc.; 1998. p. 595–628.
[171] Goycoolea F, Arguelles-Monal W, Peniche C, Higuera-
Ciapara I. Chitin and chitosan. In: Doxastakis G,
Kiosseoglou V, editors. Novel macromolecules in food systems. Developments in food science, vol. 41. Amsterdam: Elsevier; 2000. p. 265–308.
[172] Arguelles–Monal W, Cabrera G, Peniche C, Rinaudo M.
Conductimetric study of the interpolyelectrolyte reaction between chitosan and polygalacturonic acid. Polymer
2000;41:2373–8.
[173] Strand SP, Danielsen S, Christensen BE, Varum KM.
Influence of chitosan structure on the formation and stability of DNA–Chitosan polyelectrolyte complexes.
Biomacromolecules 2005;6:3357–66.
[174] Zang Y, Guan Y, Zhou S. Single component chitosan hydrogel microcapsule from a layer-by-layer approach.
Biomacromolecules 2005;6:2365–9.
[175] Berth G, Voigt A, Dautzenberg H, Donath E, Moehwald
H. Polyelectrolyte complexes and layer-by-layer capsules from chitosan/chitosan sulphate.
Biomacromolecules
2002;3:579–90.
[176] Chung TW, Yang J, Akaibe T, Cho KY, Nah JW, Kim SI, et al. Preparation of alginate/galactosylated chitosan scaffold for hepatocyte attachment. Biomaterials 2002;23:
2827–34.
[177] Lee KY, Park WH, Ha WS. Polyelectrolyte complexes of sodium alginate with chitosan or its derivatives for microcapsules. J Appl Polym Sci 1997;63:425–32.
[178] Bartkowiak A, Hunkeler D. Alginate-oligochitosan microcapsules: a mechanistic study relating membrane and capsule properties to reaction conditions. Chem Mater
1999;11:2486–92.
[179] Bartkowiak A, Hunkeler D.
Alginate-oligochitosan microcapsules. II. Control of mechanical resistance and permeability of the membrane. Chem Mater 2000;12:
206–12.
[180] Wei YC, Hudson SM, Mayer JM, Kaplan DL. The crosslinking of chitosan fibers. J Polym Sci A Poly Chem
1992;30:2187–93.
[181] Welsh ER, Price RR. Chitosan cross-linking with a watersoluble, blocked diisocyanate. 2. Solvates and hydrogels.
Biomacromolecules 2003;4:1357–61.
[182] Roy SK, Todd JG, Glasser WG. Crosslinked hydrogel beads from chitosan. US Patent 5,770,712; 1998.
[183] Baran ET, Mano JF, Reis RL. Starch–Chitosan hydrogels prepared by reductive alkylation cross-linking. J Mater Sci
Mater Med 2004;15:759–65.
[184] (a) Hirano S, Yamaguchi R, Fukui N, Iwata M. A chitosan oxalate gel: its conversion to an N -acetylchitosan gel via a chitosan gel. Carbohydr Res 1990;20P1:
145–9;
(b) Yamaguchi R, Hirano S, Arai Y, Ito T. Chitosan salt gels thermally reversible elation of chitosan. Agric Biol
Chem 1978;42:1981–2.
[185] Desai KGH, Park HJ. Encapsulation of vitamine C in tripolyphosphate cross-linked chitosan microsperes by spray drying. J Microencapsulation 2005;22:179–92.
[186] Lee S-T, Mi F-L, Shen Y-J, Shyu S-S, Tang I-H. The copper (II) uptake by chitosan-tripolyphosphate chelating resin and related kinetic studies. In: Chen RH, Chen
HC, editors.
Advances in chitin science, vol.
3.
Taiwan: Publis National Taiwan Ocean University; 1998.
p. 475–80.
[187] Ko MJ, Jo WH, Kim HC, Lee SC. Miscibility of chitosans/ polyamide 6 blends. Polym J 1997;29:997–1001.
[188] Hosokawa J, Nishiyama M, Yoshihara K, Kubo T.
Biodegradable film derived from chitosan and homogeneized cellulose. Ind Eng Chem Res 1990;29:800–5.
[189] Hasegawa M, Isogai A, Kuga S, Onabe F. Preparation of cellulose–chitosan blend film using chloral/dimethylformamide. Polymer 1994;35:983–7.
[190] Mucha M, Piekielna J, Wieczorek A. Characterization and morphology of biodegradable chitosan/synthetic polymer blends. Macromol Symp 1999;144:391–412.
[191] Abou-Aiad THM, Abd-El-Nour KN, Hakim IK, Elsabee
MZ. Dielectric and interaction behavior of chitosan/ polyvinyl alcohol and chitosan/polyvinyl pyrrolidone blends with some antimicrobial activities. Polymer 2005;47:
379–89.
[192] Wang S-F, Shen L, Zhang W-D, Tong Y-J. Preparation and mechanical properties of chitosan/carbon nanotubes composites. Biomacromolecules 2005;6:3067–72.
[193] Roberts GAF. Chitin chemistry. London: MacMillan
Press; 1992.
[194] Morimoto M, Saimoto H, Shigemasa Y. Control of functions of chitin and chitosan by chemical modifications.
Trends Glycosci Glycotech 2002;14:205–22.
[195] (a) Sashiva H, Yamamori N, Ichiinose Y, Sunamoto J, Aiba
S-I. Michael reaction of chitosan with various acryl reagents in water. Biomacromolecules 2003;4:1250–4
(b) Bartkowiak AW, Roberts GAF. Preparation and properties of novel N -alkylchitosan derivatives. In:
Karniki SZ, editor. Chitin world. Wirtschaftsverlag
NW, Bremerhaven, Germany; 1994. p. 119–126.
[196] (a) Rinaudo M, le Dung P, Milas M. A new and simple method of synthesis of carboxymethylchitosans. In:
Brine CJ, Sandford PA, Zikakis JP, editors. Advances in chitin and chitosan. London and New York:
Elsevier; 1992. p. 516–25;
(b) Rinaudo M, Le Dung P, Gey C, Milas M. Substituent distribution on O , N -carboxymethylchitosans by
1
H and
13
C NMR. Int J Biol Macromol 1992;14:122–8;
(c) Le Dung P, Milas M, Rinaudo M, Desbrie`res J. Water soluble derivatives obtained by controlled chemical modification of chitosan. Carbohydr Polym 1994;24:
209–14.
[197] Muzzarelli RAA, Muzzarelli C, Cosani A, Terbojevich M.
6-oxychitins, novel hyaluronan-like regiospecifically carboxylated chitins. Carbohydr Polym 1999;39:361–7.
[198] Terbojevich M, Carraro C, Cosani A. Solution studies of chitosan 6O -sulfate. Makromol Chem 1989;190:2847–55.
[199] Naggi AM, Torri G, Compagnoni T, Casu B. Synthesis and physico-chemical properties of a polyampholyte chitosan 6sulfate. In: Muzzarelli RAA, Jeuniaux C, Gooday GW, editors. Chitin in nature and technology. New York:
Plenum Publishing Corporation; 1986. p. 371–7.
[200] Holme KR, Perlin AS. Chitosan N -sulfate. A water-soluble polyelectrolyte. Carbohydr Res 1997;302:7–12.
[201] Heras A, Rodriguez NM, Ramos VM, Agullo E.
N -methylene phosphonic chitosan: a novel soluble derivative. Carbohydr Polym 2000;44:1–8.
[202] Ramos VM, Rodriguez NM, Diaz MF, Rodriguez MS,
Heras A, Agullo E.
N -methylene phosphonic chitosan: effect of preparation methods on its properties. Carbohydr
Polym 2003;52:39–46.
[203] Wojcik G. Metal corrosion inhibiting compositions containing chitosan derivatives. USPatent 6,508,958; 2003.
[204] Ramos VM, Rodriguez NM, Rodriguez MS, Heras A,
Agullo E. Modified chitosan carrying phosphonic and alkyl groups. Carbohydr Polym 2003;51:425–9.
[205] Domard A, Rinaudo M, Terrassin C. A new method for the quaternization of chitosan. Int J Biol Macromol 1986;8:
105–7.
[206] Domard A, Gey C, Rinaudo M, Terrassin C.
13
C and
1
H
NMR spectroscopy of chitosan and N -trimethyl chloride derivatives. Int J Biol Macromol 1987;9:233–7.
[207] Domard A, Rinaudo M, Terrassin C. Adsorption of chitosan and a quaternized derivative on kaolin. J Appl
Polym Sci 1989;38:1799–806.
[208] Suzuki K, Oda D, Shinobu T, Saimoto H, Shigemasa Y.
New selectively N -substituted quaternary ammonium chitosan derivatives. Polym J 2000;32:334–8.
[209] (a) Hall LD, Yalpani MD. Formation of branched-chain, soluble polysaccharides from chitosan. J Chem Soc
Chem Commun 1980:1153–4;
(b) Yalpani MD, Hall LD. Some chemical and analytical aspects of polysaccharide modifications. 3. Formation of branched-chain, soluble chitosan derivatives.
Macromolecules 1984;17:272–81.
[210] Holme KR, Hall LD. Preparation and characterization of
N -[2-(glycosyloxy)-ethyl] chitosan derivatives. Carbohydr
Res 1992;225:291–306.
[211] Harris JM, Struk EC, Case MG, Paley MS, Yalpani M,
Van Alstin JM, et al. Synthesis and characterization of
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632 631 poly(ethylene glycol)derivatives. J Polym Sci Poly Chem Ed
1984;22:341–52.
[212] Aiba S-I, Minoura N, Fujiwara Y. Graft copolymerization of amino acids onto partially deacetylated Chitin. Int J Biol
Macromol 1985;7:120–1.
[213] Holme KR, Hall LD. Chitosan derivatives bearing
C-10–alkyl glycoside branches: a temperatureinduced gelling polysaccharide. Macromolecules 1991;24:
3828–33.
[214] Kohgo O, Ishii S, Nishimura S-I, Kurita K. Amphiphilic polysaccharides from chitosan by regioselective chemical modification. In: Brine CJ, Sandford PA, Zikakis JP, editors. Advances in chitin and chitosan. London and New
York: Elsevier; 1992. p. 526–32.
[215] Hirano S, Hayashi K-I, Hirochi K. Some N -acyl derivatives of O -carboxymethylchitosan. Carbohydr Res 1992;225:
175–8.
[216] Desbrie`res J, Martinez C, Rinaudo M. Hydrophobic derivatives of chitosan: characterization and rheological behaviour. Int J Biol Macromol 1996;19:21–8.
[217] Muzzarelli RAA, Frega N, Miliani M, Muzzarelli C,
Cartolari M. Interactions of chitin, chitosan, N -lauryl chitosan and N -dimethylaminopropyl chitosan with olive oil. Carbohydr Polym 2000;43:263–8.
[218] Babak VG, Rinaudo M, Desbrie`res J, Vikhoreva G A,
Michalski MC. The effect of alkyl chain length of a polysoap on the surface activity of its complexes with cationic surfactants. Mendeleyev Commun 1997:149–51.
[219] Olteanu M, Mandru I, Dudau M, Peretz S, Cinteza O. the aqueous liquid/liquid interphases formed by chitosan–anionic surfactant complexes. Progr Colloid Polym Sci
2003;122:87–94.
[220] Desbrie`res J, Rinaudo M, Chtcheglova L. Reversible thermothickening of aqueous solutions of polycations from natural origin. Macromol Symp 1997;113:135–49.
[221] Rinaudo M, Auzely R, Vallin C, Mullagaliev I. Specific interactions in modified chitosan systems. Biomacromolecules 2005;6:2396–407.
[222] Eli W, Chen W, Xue Q. The association of anionic surfactants with b -cyclodextrins. An isothermal titration calorimeter study. J Chem Thermodyn 1999;31:1283–96.
[223] Rekharsky MV, Inoue Y. Complexation thermodynamics of cyclodextrins. Chem Rev 1998;98:1875–917.
[224] Kriz Z, Koca J, Imberty A, Charlot A, Auzely-Velty R.
Investigation of the complexation of (+)-catechin by b -cyclodextrin by combination of NMR, microcalorimetry and molecular modelling techniques. Org Biomol Chem
2003;1:2590–5.
[225] Sakairi N, Nishi N, Tokura S. Cyclodextrin-linked chitosan: synthesis and inclusion complexation ability. In:
El-Nokaly MA, Soini HA, editors. Polysaccharide applications: cosmetics and pharmaceuticals, ACS Symposium
Series. vol. 737; 1999. p. 68–84.
[226] Auzely R, Rinaudo M. Controlled chemical modifications of chitosan characterization and investigation of original properties. Macromol Biosci 2003;3:562–5.
[227] Auzely-Velty R, Rinaudo M. Chitosan derivatives bearing pendant cyclodextrin cavities: synthesis and inclusion performance. Macromolecules 2001;34:3574–80.
[228] Auzely-Velty R, Rinaudo M. New supramolecular assemblies of a cyclodextrin grafted chitosan through specific complexation. Macromolecules 2002;35:7955–62.
632
ARTICLE IN PRESS
M. Rinaudo / Prog. Polym. Sci. 31 (2006) 603–632
[229] Charlot A, Auzely-Velty R, Rinaudo M. Specific interactions in model charged polysaccharide systems. J Phys
Chem B 2003;107:8248–54.
[230] Thanou M, Junginger HE. Pharmaceutical applications of chitosan and derivatives. In: Dumitriu S, editor. Polysaccharides. Structural diversity and functional versatility.
2nd ed. New York: Marcel Dekker Publ.; 2005. p. 661–77.
[231] Ravi Kumar MNV, Muzzarelli RAA, Muzzarelli C,
Sashiwa H, Domb AJ. Chitosan chemistry and pharmaceutical perspectives. Chem Rev 2004;104:6017–84.
[232] Illum L, Davis S. Chitosan as a delivery system for the transmucosal administration of drugs. In: Dumitriu S, editor. Polysaccharides. Structural diversity and functional versatility. 2d ed. New York: Marcel Dekker Publ.; 2005.
p. 643–60.
[233] Kotze´ AF, Hamman JH, Snyman D, Jonker C, Stander M.
Mucoadhesive and absorption enhancing properties of N trimethyl chitosan chloride. In: Muzzarelli RAA, Muzzarelli C, editors. Chitosan in pharmacy and chemistry.
Grottammare (Italy): ATEC; 2002. p. 31–40.
[234] (a) Hamman JH, Kotze´ AF. Paracellular absorption enhancement across intestinal epithelia by N -trimethyl chitosan chloride. In: Muzzarelli RAA, Muzzarelli C, editors. Chitosan in pharmacy and chemistry. Grottammare (Italy): ATEC; 2002. p. 41–50;
(b) Venter JP, Kotze´ AF, Auze´ly-Velty R, Rinaudo M.
Synthesis and evaluation of the mucoadhesivity of a
C D -chitosan derivative. Int J Pharm 2006;313:36–42.
[235] (a) Miwa A, Ishibe A, Nakano M, Yamahira T, Itai S,
Jinno S, et al. Development of novel chitosan derivatives as micellar carriers of taxol. Pharm Res 1998;15:
1844–50;
(b) Liu W, Sun SJ, Zhang X, De Yao K. Self-aggregation behaviour of alkylated chitosan and its effect on the release of a hydrophobic drug. J Biomater Sci Polym
Edn 2003;14:851–9.
[236] Liu W, Zang X, Sun SJ, Sun GJ, Yao KD, Liang DC, et al.
N -alkylated chitosan as a potential nonviral vector for gene transfection. Bioconjug Chem 2003;14:782–9.
[237] Ouchi T, Murata J-I, Ohya Y. Gene delivery by quaternary chitosan with antennary galactose residues. In: El-Nokaly
MA, Soini HA, editors. Polysaccharide applications: cosmetics and pharmaceuticals. ACS Symposium Series
737; 1999. p. 15–23.
[238] El Zein AR, Dabbarh F, Chaput C. Injectable self-setting calcium phosphate cement. In: Muzzarelli RAA, Muzzarelli C, editors. Chitosan in pharmacy and chemistry.
Grottammare (Italy): ATEC; 2002. p. 365–70.
[239] Yi H, Wu L-Q, Bentley WE, Ghadssi R, Rubloff GW,
Culver JN, et al. Biofabrication with chitosan. Biomacromolecules 2005;6:2881–94.
[240] Pospieszny H, Struszczyk H, Chirkov SN, Atabekov JG.
New applications of chitosan in agriculture. In: Karniki SZ, editor. Chitin world. Bremerhaven, Germany: Wirtschaftsverlag NW; 1994. p. 246–54.
[241] Doares SH, Syrovets T, Weiler EW, Ryan CA. Oligogalacturonides and chitosan activate plant defensive genes through the octadecanoid pathway. Proc Natl Acad Sci
1995;92:4095–8.
[242] Kanke M, Katayama H, Tsuzuki S, Kuramoto H.
Application of chitin and chitosan to pharmaceutical preparations. I. Film preparation and in vitro evaluation.
Chem Pharm Bull 1999;37:523–5.
[243] Li Z, Ramay HR, Hauch KD, Xiao D, Zhang M.
Chitosan–alginate hybrid scaffolds for bone tissue engineering. Biomaterials 2005;26:3919–28.
[244] Wang L, Khor E, Wee A, Lim LY. Chitosan–alginate PEC membrane as a wound dressing: assessment of incisional wound healing. J Biomed Mater Res 2002;63:610–8.
General references
[1] Muzzarelli RAA, Pariser ER. In: Proceedings of the first international conference on Chitin/chitosan. Cambridge
(MA,. USA): MIT Sea grant Program; 1978.
[2] Zikakis JP. Chitin, chitosan and related enzymes. Orlando:
Academic Press, Inc.; 1984.
[3] Muzzarelli RAA, Jeuniaux C, Gooday GW. Chitin in nature and technology. New York: Plenum Publishing Corporation;
1986.
[4] Skjak-Braek G, Anthonsen T, Sandford P. Chitin and chitosan. Sources, chemistry, biochemistry, physical properties and applications. London and New York: Elsevier; 1989.
[5] Brine CJ, Sandford PA, Zikakis JP. Advances in chitin and chitosan. London and New York: Elsevier; 1992.
[6] Roberts GAF. Chitin chemistry. London: MacMillan Press;
1992.
[7] Karniki SZ.
Chitin world.
Bremerhaven, Germany:
Wirtschaftsverlag NW; 1994.
[8] European Chitin Society. Advances in chitin science, vol. 1,
1996, vol. 2, 1998, vol. 3, 1999, vol. 4, 2000, vol. 5, 2003, vol.
6, 2003, vol. 7, 2004, Vol. 8, 2005.
[9] Stevens WF, Rao MS, Chandrkrachang S. Chitin and chitosan—environmental friendly and versatile biomaterials.
The proceedings of the second Asia Pacific Symposium, 1996.
[10] Muzzarelli RAA. Chitin enzymology. Grottammare (Italy):
ATEC; 2001.
[11] Muzzarelli RAA, Muzzarelli C. Chitosan in pharmacy and chemistry. Grottammare (Italy): ATEC; 2002.
